Later, Gohan, a hero who has achieved the identity as the Great Saiyan Man, attends a tournament. When it is the Great Saiyan Mans turn to compete, he turns into his Super Saiyan form and his disguise is blown off. Everyone is amazed that a nerd, Gohan, is the Great Saiyan Man. All of a sudden, Spopobitch and Yamu come out of nowhere and absorb Gohan's energy into a "lamp" to revive Boo. Kaio-shin and his partner, trying to prevent Babi-di's and Dabura's plot to reactivate Boo, allow this to happen so that he could follow the energy stealers to their hideout. (Babi-di's goal is to destroy all life just for the fun of it.) But, he revives Gohan first. The Saiyan warriors decide to go as well. A fight follows. Darbura turns Kuririn and Piccolo into stone and Kaio-shin's partner is killed. The Z warriors learn that Kuririn and Piccolo will return to normal once Darbura dies. In battle, Vegeta is turned into Babi-di's slave and an "M" appears on Vegeta's forehead. His energy is used to reactivate Boo. Boo betrays Dabura and eats him. Thus, Piccolo and Kuririn are returned too normal. Majin Vegeta beats Goku, and then goes to fight Boo. Upon failing, Vegeta self-destructs and dies. Afterwards, Bulma gathers the dragonballs to revive all those killed since the fighting tournament. In the fights later on, Goku gets angry enough and reaches Super Saiyan form 3 for the first time! (In stage three, Goku has long hair and is more powerful than ever.) Gohan also heads to Kaio-shin's planet, pulls out the Z sword, and trains under Rou Kaoi-shin. Goten and Trunks train as well to get stronger. From Goku, they learn the art of fusion to fuse to become one, becoming Gotenks!

However, our heroes are still no match for Boo. Although Dabura's, the Prince of Darkness (Babi-di's associate who looks like a devil), and Babi-di's (a little ugly sorcerer with tiny hairs growing out of his body) other minions are killed, Buu gets stronger. Buu later revolts against his master (Babi-di) and kills him. Before their deaths, the villainous Babi-di and Dabura have cast a spell that turned Vegeta evil. However, in addition with fighting against Goku, the evil Vegeta also fought Boo. Although defeated by Boo, Vegeta later turns good again. It is here that Vegeta finally becomes one of the good guys. (In previous times, Vegeta only aids our heroes to assure that Goku lives long enough for him to kill Goku. But, he never attempted to kill Goku since the early battle against him in the Vegeta Series. Next Boo separates into two forms one good and the other evil. Evil Boo defeats good Boo and turns him into a cookie, and eats him. From this method, the evil Boo gains the good Boo's powers and changes into a stronger form. Boo, previously fat, is now skinnier and taller, not to mention a lot stronger. Gotenks is also stronger; he is now able to turn into Super Saiyan stage 3, like Goku. But, he is still defeated on one of his encounters with Boo and Boo engulfs SSJ3 Gotenks. Thus, Boo absorbed Gotenks' powers and becomes stronger again. He changes form again! (His "antennae" grows longer and he now wears a black vest like Gotenks'.) Piccolo is also defeated and eaten by Buu. Meanwhile, Gohan had mastered the Z sword and learned how to use his hidden powers without getting angry under training with Dai Kaio-shin. (He does not turn into his Super Saiyan form for the rest of the series at this point.) Unfortunately, he too is defeated and engulfed. Buu, now with Gohan's powers, changes form again. (He now looks like he's wearing Gohan's clothes.) With the other warriors defeated, only Goku and Vegeta are left to battle against Boo!

Goku is still dead and watches the fight through Kaio-shin's crystal ball. Seeing the unfortunate odds for our heroes, Rou Kaio-shin sacrifices his life to Goku and dies. Goku's halo disappears, and Rou Kaio-shin wakes back up with a halo over his head. Now, Goku teleports into the battle. Vegeta, still dead, is also sent into battle by the judge of death. Goku acquired a pair of special earrings from the Kaio-shins that when each one is worn by two different people, the two will permanently fuse. With Goku wearing one of the earrings and Vegeta wearing the other, the two are pulled together and fused into Vegetto. As Vegetto's turn to fight Boo, Boo seems to be no match for Vegetto, but Vegetto purposely gets eaten by Boo to save the other Z warriors. This cancelled the effects of the permanent fusion in Vegetto and they turn back into Goku and Vegeta.

>Next, Boo undergoes another form change and temporarily becomes very muscular as he stands still in pain through the form change. Goku and Vegeta are now inside of Boo's organs. They find Trunks, Goten, Gohan, and Piccolo, and rescue them by carrying them out of one of Boo's pores. As they leave Buu, the warriors grow bigger and are restored to their normal size. Fat Boo, the good Boo, also escapes from Boo's body. The evil Boo, still "puffy" and bulky, is undergoing his form change to restore to his original form. (The Kaio-shins cursed him into his previous fat looking form for destroying their people.) Afterwards, he is little and short. Next, evil Boo does a giant fireball and blows up Earth! Luckily, Goku had enough time and teleported himself and his comrades to another planet. Later, the Namek dragonballs are gathered and a wish is made to restore the earth. The little Boo also met with the fat Boo. They fight, but the good Boo is once again defeated.

Eventually, Goku and Vegeta are fighting Boo. Vegeta stalls Boo as Goku gathers the energy to do a Genki Dama. While Vegeta is getting kicked around by Boo, Piccolo, Gohan, Goten, and Trunks are on earth trying to convince the earthlings to raise their hands so that their energy will be given to aid Goku strengthen his genki dama. Because no one on earth listens to the heroes, a new approach is taken. Satan is contacted for help. Because of his fame, he tells the world to raise their hands to show their appreciation to Satan. With everyone's hand raised, energy is transferred to Goku and now he has enough power to destroy Boo. With a single genki dama, Boo is destroyed.