While searching in the deep mountainside for the Dragon Balls, which grant any wish to the one who collects all seven, a teenage girl named Bulma meets Son Goku, a naïve young boy with a monkey tail and fantastic martial arts skills who has never seen another human aside from his Grandfather. Seeing how strong Goku is and his possession of the four-star Dragon Ball, Bulma asks him to accompany her on the search for the remaining four Dragon Balls using a device she created that detects them. Soon after Bulma is abducted by a pterodactyl, but Goku easily rescues her using his Nyoi-bō.

With nightfall upon them, Bulma opens a house from a Hoipoi Capsule, which can shrink inanimate objects down to pocket sized capsules. After he sees artificial lighting and television for the first time, Bulma decides to help Goku bathe as he has never heard of a bath before either. She is shocked to see that his tail is actually real and then angered upon learning he is fourteen-years old, only two years younger than herself, after he walks in on her bathing. When he wakes up in the morning, Goku climbs into Bulma's bed to use her crotch as a pillow like he used to with his Grandfather, but noticing her crotch is "not as big," he removes her panties and screams in shock waking her up. Unaware of what he has done, Bulma assumes Goku had a nightmare and was referring to the Dragon Balls when he said "You've lost your balls."

While exercising in the morning waiting for Bulma to get ready, Goku meets a sea turtle that has been wondering around lost for the past year hoping to get back to the sea. Goku decides to help him return, but Bulma is initially against it until realizing Goku still has his Dragon Ball. A giant anthropomorphic bear tries to stop them so he can eat the turtle, but Goku easily defeats him with his Jan-Ken attack. When they arrive at the sea, the turtle asks them to wait while he gets them a reward; he returns with an old man riding on his back.

Kame-Sen'nin, the Turtle Hermit, gives Goku the flying cloud Kinto'un as a reward. When Bulma asks for one as well, the old man says he might have something else for her if she lets him see her panties. A blushing Bulma agrees and quickly flashes him. While Kame-Sen'nin is pondering what to give her, Bulma notices he has the three-star Dragon Ball around his neck and asks for that. When he shows reluctance, she flashes him again. Back at their house, Bulma is mortified to learn she did not have any panties on and then shoots Goku when he admits to removing them. Three days later the two arrive in a village that should have a Dragon Ball, but the residents are nowhere to be seen.

When Goku breaks into a house, a man attacks him believing him to be "Lord Oolong", a "demon" shape-shifter who's kidnapped other villages' girls, and claimed the man's daughter to be his future wife. In exchange for the six-star Dragon ball, Bulma plans to have Goku dress up as the young girl so he will be taken back to Oolong's lair and can rescue the others. When Goku accidentally reveals himself, an angered Oolong transforms into a large bull.

After trying to unsuccessfully get Goku to back down, Oolong calls a timeout and runs away to turn back into his normal anthropomorphic pig self, as he can only transform for five minutes and requires a minute to charge. After returning and seeing Goku's strength, Oolong runs away again but is caught and forced to return the girls he's kidnapped. Seeing his transforming as useful, Bulma takes Oolong with her and Goku on their journey.

After he learns their next destination is Fry-Pan Mountain, home of Gyū-Maō or the "Ox King," Oolong tries to escape but his perversion gets him caught. Having run out of gas, Bulma realizes she lost her capsules, forcing them to walk. The trio end up in a desert, where a young man named Yamcha and his cat-like companion Pu'ar approach them.

When Yamcha and Pu'ar attempt to rob Goku and Oolong of their money and capsules, Oolong recognizes Pu'ar from Shapeshifter School. After being surprised by Nyoi-bō, Yamcha knocks Goku back with his Rōga Fūfūken, while Goku connects with his Jan-Ken attack. Just as Goku's about to pass out from hunger, Yamcha sees Bulma and has to retreat due to his nervousness around girls.

At night the trio rest in Oolong's recreational vehicle capsule, when Yamcha and Pu'ar overhear Goku explain the Dragon Balls to Oolong they shift their goal to them instead of the capsule, so Yamcha can wish to rid his fear of girls. Oolong drugs Goku and Bulma so he can molest her while she sleeps, when Pu'ar enters transformed as Goku, forcing Oolong to transform into Bulma. As Pu'ar lures Oolong outside, Yamcha removes the covers on the bed mistaking the sleeping Bulma's breasts to be the Dragon Balls. The robbers are forced to retreat.

Forced to keep watch all night, Oolong couldn't clean Bulma's clothes leaving only a Playboy Bunny outfit for her to wear. Yamcha and Pua'r attack again destroying the vehicle with a panzerfaust, but when Goku wins in an exchange and knocks Yamcha's tooth out, he retreats. Realizing it would be easier to allow them to collect the remaining Dragon Balls before stealing them, Yamcha apologizes and gives the trio a car capsule that he planted a tracking device on.

Two days later the trio arrive at the flame-surrounded Fry-Pan Mountain, which has Gyū-Maō's castle atop it, wherein the Dragon Ball lies. Unable to enter it even using Kinto'un, Gyū-Maō catches them, but recognizes the cloud as his martial arts master's.

Gyū-Maō notices Nyoi-bō and informs Goku that he and Goku's grandfather were martial arts students together under Kame-Sen'nin. The Ox King asks Goku to retrieve the Bashō-sen from Kame-Sen'nin so he can use it to put out the fire surrounding his castle, and to take his daughter Chi-Chi along with him. Goku agrees in exchange for the Dragon Ball. As Chi-Chi gets onto Kinto'un she pulls Goku's tail, causing him to lose his strength, with Yamcha secretly watching and learning this weakness. The two kids find Kame-Sen'nin's island in the middle of the ocean.

Kame-Sen'nin agrees to lend the duo the Bashō-sen but only if he can feel Bulma's breasts, to which Goku agrees. However, Kame-Sen'nin realizes he threw the fan away after spilling wonton soup on it and therefore offers to put the fire out personally.

After arriving back at Fry-Pan Mountain, Goku catches Bulma up on the deal with Kame-Sen'nin, to which she is livid but agrees because of the Dragon Ball, and only after he puts the fire out. Kame-Sen'nin bulks up his scrawny frame substantially and performs his signature technique the Kamehameha, which focuses his dormant energy into a single blast. While it puts the fire out, it also destroys the castle.

Goku asks Kame-Sen'nin to teach him the Kamehameha, but the master informs him it takes 50 years to learn. However, Goku manages to fire a little one and Kame-Sen'nin learns who his grandfather is and of his passing. Kame-Sen'nin offers Goku to move in with him and train, to which Goku agrees after they find the remaining Dragon Balls. Bulma forces Oolong to transform into herself and let Kame-Sen'nin feel him up, although Oolong encourages the old man to go further and perform Puff-Puff. Chi-Chi suggests that when Goku's old enough her father might give him "her hand," not understanding, Goku states that if he'll give him something, he's sure to accept.

Running low on fuel, the trio stop at a town where the residents all seem afraid of them. When Bulma buys new clothes, it turns out they were afraid because they assumed she was in the "Rabbit Mob" due to her Playboy Bunny outfit. When two members of the mob flirt with Bulma she has Goku beat them up. One of them calls their master to save them.

The Rabbit Gang boss, an anthropomorphic rabbit, approaches and asks Bulma to shake hands, when she does she turns into a carrot. Goku starts using Nyoi-bō, but the boss threatens to eat her if he doesn't stop and has his lackeys beat him. Forced to help, Pu'ar transforms into a bird and snatches the carrot while Yamcha saves Goku so he can use his stick and force the boss to transform Bulma back. Goku uses Nyoi-bō to take the three gang members to the moon, where they're seen making rice cake like the folktale.

En route to the last Dragon Ball, the trio are attacked and all but Goku's Dragon Ball are stolen by an unnamed woman and a humanoid dog named Soba. Yamcha and Pu'ar offer the trio a ride to the lair of the enemies' leader, Pilaf who wants to wish for world domination, using Bulma's radar, where all five travelers follow arrows on the floor into a trap.

Realizing one of their captees must have the only remaining Dragon Ball on their person, Pilaf threatens them to simply hand it over or he will do something "nasty." When Bulma mocks him, Pilaf has a mechanical arm bring Bulma to him and blows her a kiss. When she expresses relief and offends him by naming the things she thought he was going to do, he sends her back to the trap room. The enemies knock all the captees out with sleeping gas, obtain the last ball, and summon the wish-granting Shenlong. Meanwhile, Goku blasts a hole through the wall with a Kamehameha and Pu'ar and Oolong transform into bats and escape to stop them.

Realizing they're too late to stop the summoning, Oolong instead interrupts Pilaf's wish and asks for a pair of panties, which he is granted with the Dragon Balls scattering across the world. The quintet are transferred into a steel room with a shatterproof glass ceiling and Bulma explains that the Dragon Balls turn to stone and are untraceable for a year. Pilaf informs them that when the sun rises they will be cooked alive in the sealed room.

Goku tells the others how a monster comes out on the night of a full moon and that his Grandfather always warned him not to look at the full moon. Something Goku disobeyed the night Gohan died from being stepped on by said monster, although Goku can't remember any of it. His friends suspect Goku is the monster but before they could tell him not to look at the moon, it is too late and he transforms into a giant ape breaking through the ceiling.

Goku in his giant ape form destroys the lair in a rage, including Pilaf and company's fleeing plane, not heeding to his friends' pleas to stop. Pu'ar reminds Yamcha of Goku's weakness, with the later grabbing Goku's tail, paralyzing the monster, while Pu'ar transforms into scissors to cut it off. Goku transforms back and sleeps.

The friends decide not to inform Goku he's the one who killed his Grandfather, and state that without the tail he'll never transform again. As Bulma laments not being able to wish for a boyfriend and Yamcha seems to be over his fear of girls, the two realize they can be an item. Not needing a wish anymore, Bulma gives Goku her radar to find his Grandpa's ball in a year's time, as he is going to train under Kame-Sen'nin while the others go to the city.

After retrieving his belongings from home, Goku travels to Kame-Sen'nin's island asks to be trained. In order to be accepted as a pupil, Kame-Sen'nin asks Goku to find him an attractive girl like Bulma. The hermit gets dressed in a suit and prepares champagne in preparation, but when Goku arrives he has brought a very large woman.

With Goku having brought another girl, a hiding Kame-Sen'nin approves from a distance and accepts Goku as his pupil, giving him his first exercise: retrieve the girl's panties. When Goku returns explaining the girl is not wearing any, the hermit decides to approach for a look. Seeing that the girl is a mermaid, Kame-Sen'nin asks instead to feel her breasts before she punches him and swims off. A bald boy approaches on a boat and asks to become a pupil, initially refused, Kame-Sen'nin changes his mind when Kuririn offers a dirty magazine. Believing Kuririn to know his taste, the master sends the two to find another girl.

A blonde woman is shooting back at the police chasing her until she sneezes and crashes. Goku and Kuririn see a brunette woman named Lunch asking for help and Goku beats the guys approaching her up, not realizing they are policemen. The two boys then take the girl back to Kame-Sen'nin's.

Lunch accepts to live on the island as she is being chased by police, assuming from a bag of money that she robbed a bank or train. She tells Kuririn that she changes personalities when she sneezes, although it doesn't seem to be heard as Kame-Sen'nin immediately and loudly approves of Lunch and accepts the boys as pupils. He invites Lunch to train as well, giving her a uniform to put on, which turns out to be lingerie. A fly causes her to sneeze and turn into her blonde personality, who is angered at the outfit and shoots the men, before quickly sneezing again and apologizing.

Having decided that his island isn't big enough for training, Kame-Sen'nin turns his house into a capsule and they relocate to a bigger one and immediately begin training. After having them run a 100-meter dash, Kuririn with 10.4 seconds and Goku 8.5, the master demonstrates a 5.6 time himself and tells them to become masters of martial arts they will need to break the "human limit" and run it in five seconds.

Kame-Sen'nin writes the kanji for turtle on a rock and throws it off a cliff, telling the boys that whoever brings the rock back is the winner and only the winner will get dinner; if no one returns after 30 minutes, neither will eat. Kuririn tries to trick Kame-Sen'nin by finding a similar rock and writing the kanji himself, but the master sees through it. Goku finds the real one by scent, but Kuririn tricks him with the fake and wins the contest. However, everyone but Goku came down with food poisoning and training was halted for three days.

The boys finally begin their training under Kame-Sen'nin, but the "early morning" training turns out to be delivering milk. However, they must do it on foot for the entire island, including across quicksand, raging rivers, and up mountains of stairs. During which they learn that the master plans to have them enter the Tenka'ichi Budōkai or "Strongest Under the Heavens Martial Arts Tournament" in eight months.

Goku and Kuririn begin their "morning" routine of training which consists of farm work; specifically plowing entire fields with their bare-hands. After breakfast comes training of the mind, where Kame-Sen'nin has them read erotic literature, followed by a nap, and then construction work. When the students complain about not learning any fighting techniques, the master points out an enormous boulder and tells them he'll only teach them to fight when they can move it. Following swimming laps while fleeing from a shark, the boys are then tied to a tree while Kame-Sen'nin knocks a beehive for them to dodge its angry inhabitants. At the end of the day they learn they will be doing these tasks everyday until the tournament, but wearing 20 kilo turtle shells.

Through the months Goku and Kuririn continue their training, until, with the tournament only a month away, they show Kame-Sen'nin that they can now move the boulder and ask for fighting training. However, the master reveals that he was only joking about the boulder and has nothing more to teach them, but now they will be wearing 40 kilo turtle shells during the same training. With only a day until the tournament, the boys and Kame-Sen'nin travel to the site of the Tenka'ichi Budōkai.

After Kame-Sen'nin gives Goku and Kuririn their fighting uniforms, he informs them that they must pass the qualifying rounds to become one of the final eight participants in the Tenka'ichi Budōkai proper, and that he can't accompany them but will be in the audience. To win one must knock their opponent unconscious or out of the ring, or make them concede. Killing and weapons are not permitted, and if there is no winner after one minute judges will choose the victor. Kuririn is worried because they never received actual training, but after his match Goku realizes they are much stronger than they think and warns him not to use his full strength. However, Kuririn's opponent turns out to be one of his fellow pupils from Orin Temple who used to bully him, so Goku tells him to give one shot at full power leading to Kuririn's win at his own surprise.

Kame-Sen'nin's training proves very effective as Goku and Kuririn pass the qualifying rounds and advance to the finals. Goku reunites with Yamcha who has also qualified, but who expresses doubt whether or not he could beat Goku or Kuririn. Bulma, Oolong and Pu'ar bump into Kame-Sen'nin in the audience.

After greeting Bulma, Oolong and Pu'ar, the boys must assemble with the other finalists, while Bulma notices Kame-Sen'nin has disappeared. The eight finalists draw lots to determine the matches, which have similar rules to the qualifiers but no time limit and when someone is knocked down, they lose if the announcer finishes a ten-count before they get up. Kuririn is in match one against Bacterian, a smelly obese man who has never bathed in his life. The second match is Yamcha versus an old man named Jackie Chun. The third match sees the shy Namu fight the beautiful women Ran Fuan. Goku is in match four against Giran, an anthropomorphic dinosaur.

The 21st Tenka'ichi Budōkai commences with Bacterian vs. Kuririn, who is the youngest-ever contestant. Bulma notes that Kame-Sen'nin is missing his pupil's match. Following Bacterian's stinky breath, stinky finger, and fart combination Kuririn is paralyzed by the smell and the announcer begins a ten-count. However, Goku yells to Kuririn explaining that the stench is only psychological to him because he has no nose and therefore can't actually smell it. Revived Kuririn dodges Bacterian's spits of phlegm and delivers a head-kick, before farting in his face and winning the match.

The boys try in vain to see if Kame-Sen'nin was watching, although Goku says he can still smell him nearby. The second match of Yamcha vs. Jackie Chun begins, with the latter easily dodging all the former's attacks. After dodging the Rōga Fūfūken, Jackie simply swats at the air sending a gust of wind that knocks Yamcha out of the ring, winning the match.

As the third match is about to begin, Jackie Chun sees Namu concentrating and takes a look into his mind, seeing Namu's village suffering from a drought and Namu stating he will enter the Tenka'ichi Budōkai to win the prize money and buy water. The match starts with Ran Fuan flirting with Namu and attacking him with a powerful combination as he blushes. But when Namu is about to counter, Ran Fuan screams and cries even after he gently taps her, and delivers a blow herself as he apologizes. Namu then resolves that he must no longer look at her as a woman and attacks, however, Ran Fuan strips down to her underwear causing him to retreat in embarrassment. But upon reaching the edge of the ring, Namu closes his eyes and knocks Ran Fuan out to win. Noticing Jackie Chun's reaction to the stripping, Yamcha suspects that he is Kame-Sen'nin.

With match four set to begin, Goku is missing, sending the other contestants into a search to find him and wake him from his nap. After suffering a blow due to his naïvete that sends him smashing into the wall, Goku launches Giran out of the ring, only for the monster to fly back using his wings; a contestant must touch the ground to be ruled out. Giran then spits a material he calls Lassoo-in' Gum from his mouth, which wraps around Goku's body, preventing him from moving.

With Goku unable to move, Giran attempts to win by throwing him out of bounds, just like Goku tried to do to him. Goku uses Kinto'un to fly back into the ring. However, after Giran objects claiming the cloud is an outside tool, unlike his own wings and Lassoo-in' Gum which are parts of his body, the announcer says they will only allow its use once. Aiming to hit Goku out of the ring once more, Giran takes a swing at him, but Goku uses his tail, which has grown back, to grab onto Giran's arm an avoid the hit. Goku then musters the strength to burst out of the Lassoo-in' Gum and tests his renewed strength on a wall, causing Giran to forfeit.

The announcer invites Goku and Kuririn to partake in an interview, while Bulma and company fear Goku might transform into a giant ape again. Goku reveals that he is actually only 12-years old, having learned how to properly count from Kame-Sen'nin's training. When asked if his tail is real, Goku drops his pants and moons everyone. When Kuririn reveals their master is Kame-Sen'nin, the audience gasps and backstage Yamcha asks Jackie Chun if he is the Turtle Hermit, but the old man denies it. When Jackie is called out and doesn't get an interview, he grabs the microphone and begins a song and dance routine, with Goku joining in. The match of Kuririn vs. Jackie then begins, with the latter dodging all the former's attacks. In return for being forced to block one, Jackie delivers a punch Kuririn couldn't even see.

After Goku's gives him a tip, Kuririn and Jackie have exchanges no one else can see, which result in Kuririn falling down. The announcer interrupts asking if they could explain what just happened. Jackie and Kuririn then give a slow demonstration of their exchanges with humorous anecdotes and even have the announcer carry them around, before the match resumes. Realizing he's physically outmatched, Kuririn throws a pair of panties on the ground and when Jackie runs after them, Kuririn kicks him flying out of bounds.

With no other option, Jackie Chun uses a Kamehameha to blast himself back into the ring. Goku and his friends recognize the attack and the announcer states that supposedly only Kame-Sen'nin could perform it, with Yamcha proud of himself for his suspicion. Now desperate, Kuririn blindly charges Jackie who leaves an afterimage of himself and knocks Kuririn out for the victory. Backstage Yamcha confronts Jackie about being Kame-Sen'nin again, this time in front of Goku and Kuririn. However, Yamcha fails in removing Jackie's hair and Goku can't smell Kame-Sen'nin over Jackie's cologne, with the next match is about to begin.

Goku begins his match against Namu by trying Jackie's afterimage technique, but it is ineffective. After more exchanges, Goku thinks up a new move; spinning so fast he forms something like a mini tornado. But just as he has Namu at the edge, he collapses from dizziness. Namu then jumps high into the air and dives back down towards Goku with his arms crossed for his Tenkū-Jiken technique.

Namu connects with his Tenkū-Jiken onto Goku's throat and it seems over. However, Goku rises at the nine count. Believing he must have missed the pressure point, Namu jumps to perform the attack again. Goku jumps up after him and gets Namu to chase him. With both now diving downwards, Goku lands first, jumps backwards, and then forward with a kick just as Namu is at ground level, sending him out of bounds for the victory.

Backstage during a 10-minute intermission, Jackie gives Namu an empty Hoipoi Capsule, tells him it can carry water and reveals his identity as Kame-Sen'nin. The Turtle Hermit explains that he had his pupils enter the tournament to test their strength, but with them far exceeding his expectations, he realized they might actually win. He believes that if one of the young boys were to win the title of Strongest Under the Heavens it would go to his head, thinking he had nothing left to learn. So to prevent this, he entered in disguise to teach them there is always someone better. Kame-Sen'nin asks Namu to disguise himself as the Turtle Hermit and then points him out to Yamcha, who then tells Goku and Kuririn he must have been mistaken.

Goku dodges Jackie's first attack, but drops his guard, allowing Jackie to kick him flying out of bounds. However, Goku is able to use his tail like a helicopter blade and flies back into the ring. When Goku stays he thought about using a Kamehameha like Jackie did, it angers the old master. Both contestants fire Kamehamehas that collide and knock both to the ground in an even exchange, must to Jackie's shock.

Jackie successfully performs a double afterimage attack, which Goku then imitates. However, the boy fools Jackie by leaving three afterimages instead of two. Jackie then performs Sui-ken landing several hits on Goku until the latter runs to a corner and turns his back to him. When Goku turns around using Kyō-ken with a vicious animal-like face it scares Jackie, allowing Goku to knock him into the wall.

Goku attacks Jackie by jumping all around, using his tail and scratching his face using Saru-ken. Angered, Jackie performs odd hand movements and sings, putting Goku to sleep with Min-Min-Ken and the announcer reluctantly begins counting. At the nine-count Bulma yells that dinner is ready and Goku wakes up, running around looking for food. Goku performs his Jan-Ken attack, but Jackie blocks it even though it was supposedly Goku's Grandpa's secret technique. Goku performs it again, but this time connects by performing rock when he said paper.

Jackie apologies to Goku and declares victory, saying he is only the second person he has had to use this technique on, the first being his Grandfather. Jackie uses Bankoku-Bikkuri-Shou, which has lightning continuously shoot out from his hands and envelope Goku. Jackie warns him that if he doesn't concede he will die. But just as he's about to give up, Goku sees the full moon and transforms into a giant ape.

As a giant monkey Goku is able to break free of the Bankoku-Bikkuri-Shou and begins destroying the arena. Yamcha tells Kuririn about Goku's transformation at the full moon with Jackie overhearing, and he and Pu'ar plan to grab his tail and cut it off like last time. However, Jackie has already begun a maximum power Kamehameha. When the blast clears everyone believes Goku has died.

Although everyone thinks Goku has died, Jackie revels he is fine as he fired his Kamehameha at the moon not Goku. When the match resumes, Jackie tries to fire a Kamehameha but has no energy left. Goku takes advantage of this and attacks sending Jackie out of bounds. Jackie lands and the audience erupts in applause for Goku. However, Jackie points out his feet; he smashed one into the stone ring, his feet having never touched out. Both fighters are out of energy, leading to just a physical match and giving Jackie an idea.

Goku and Jackie Chun charge at each other, both perform a kick, and both connect. With both contests knocked out, the announcer begins the count. When he reaches ten, neither contestant has risen. In accordance with the rules, whoever stands first and proclaims victory will be crowned the winner. Both begin to stand, Goku rises first but passes out again on his last syllable. Jackie then rises and proclaims victory as the winner of the 21st Tenka'ichi Budōkai. Jackie explains that in the end, it came down to him being taller and therefore his kick hit deeper. Goku asks Jackie if they can fight again after he's gotten stronger, to which the master agrees.

Goku and company wait for Kame-Sen'nin to appear and although he congratulates his pupils, he tells them they should not be satisfied by their performances as there is always someone better out there. The master then takes everyone out to dinner, but with Goku's appetite almost all of his prize money is spent. When Yamcha asks if they will continue to train, the boys say yes, but Kame-Sen'nin explains he has already taught them everything he can, they must train themselves from now on. Goku says he will look for his Grandpa's four-star Dragon Ball, while Kuririn is undecided and asks to stay with Kame-Sen'nin for now. Goku says good-bye and immediately sets out on his journey.