Seven years later, the Boo series begins. Gohan is now going to school at Orange Star High School and dating Mr. Satan's daughter, Videl. Krillin has married Android 18 and they have a son named Marron. Trunks is now 8 years old and spends all his time with Goten, Gohan's younger brother. Gokou is in a fighting tournament on the other side, and Trunks and Goten are being trained to fight by Vegeta and Gohan, respectively. Both Trunks and Goten can already reach the Super Saiyan level.
A great tournament is taking place on earth, the Tenkaichi Boudoukai. Many of the heroes are in it, including Piccolo, Gohan, Goten and Trunks (in disguise, as they're too young), Android 18, and Gokou (who got a day to live so he could be in the tournament.) Spopobitch and Yamu, two other competetors, use a weird lamp to drain all the energy from Gohan, then fly away. As the heroes help Gohan, a man named Kaiou-shin approches them and reveals that he is a god, like Kaiou. He says that he needs to stop Babi-di and Daruba, the former being just evil and the latter being the prince of darkness, from reviving a thing called Boo. The heroes agree to help Kaiou-shin, and they all follow Spopobitch and Yamu to find Babi-di and Daruba.

There is a lot of fighting now. The heroes destroy all of Babi-di and Daruba's minions, then Vegeta volunteers to be Babi-di's slave, believing it will make him stronger. Piccolo and Krillin are turned to stone by Daruba, but they're restored when Daruba gets killed. With the help of the now evil Vegeta, or Majin-Vegeta, Babi-di is able to revive Boo. Boo proceeds to destroy things, under the direction of Babi-di. Vegeta and Gokou fight, and Vegeta nearly kills Gokou before he regains his senses and flies off to try to beat Boo. Since he is unable to defeat Boo, Vegeta self-desructs as a last ditch effort to beat him. It doesn't work.

Next it's Gokou's turn to fight Boo, and when he reaches Super Saiyan level 3 for the first time, he gains the advantage. Then Boo kills Babi-di and splits into two parts: a good part and an evil part. The evil part eats the good part, and becomes more powerful.

All the heroes gathers at Sky Palace, except for Gohan who is training with Kaiou-shin. Gokou helps Gotan and Trunks fuse into Gotenks, then he goes to Kaiou-shin's world too. The powerful Gotenks quickly attracts the attention of Boo. Boo wants to fight Gotenks, so he waits while Gotenks trains in the Room of Spirit and Time. While he waits, he kills Chi-chi, who is being annoying.

After Gotenks and Boo fight for awhile, Piccolo blasts the room's exits to seal Boo in and save the world. Boo creates a portal, and escpaes. Gotenks powers up to Super Saiyan level 3, and then performs the same manuever. Gotenks then fights Boo, destroying Sky Palace and severely injuring Boo in the process. After Boo falls to earth, Gotenks is going to finish him but the fusion falls apart and Gotenks reverts to Gohan and Trunks. Gohan then comes back and defeats Boo, causing him to self-destruct. As Gohan, Goten, and Trunks leave, they re-encounter Boo, who didn't die after all. Goten and Trunks fuse again, but Boo absorbs Gotenks and becomes much stronger, then turns on Gohan.

During the fight, King Yemma revives Vegeta to save the world. On Kaiou-shin world, Gokou is given a pair of earings that will allow two people to fuse. Dai Kaiou-shin exhanges his life for Gokou's, and the newly alive Gokou teleports back to earth. Gokou arrives before Boo can absorb Gohan and blasts Boo into two pieces. Before Gohan can put on his earring, however, Boo absorbs him and reforms. Vegeta finds the earring that Gohan dropped, and he fuses with Gokou to make Vegetto. Vegetto beats Boo, then lets himself be absorbed to save Gohan, Goten, Trunks, and Piccolo. Once absorbed, Vegetto splits back to Gokou and Vegeta, and they leave with their friends through one of Boo's pores. Unfortunately, absorbing Vegetto has made Boo extremely powerful.

Boo shoots a large fireball to destroy the earth, and Gokou teleports those present to Kaiou-shin's planet. Boo follows, and defeats Gokou, then Vegeta. Suddenly, the good Boo erupts from inside the evil Boo. They fight.

The Namek dragonballs are gathered, and the earth, along with its people, are wished back into exsistence. On earth, the remaining heroes tell everyone to raise their hands, to help change Gokou's fireball. Once Mr. Satan raises his hands, so does everyone else.

Back on Kaiou-shin's world, Gokou is preparing a huge Genki-dama. The last wish made with the Namek dragonballs is to restore Gokou's strength, and his fireball rips Boo to shreds. At Mr. Satan's request, the Fat Boo that remains is allowed to live.

Ten years later Gokou revives the evil Boo, to fight him again, but the wish turns evil Boo into Ubuu, who isn't evil at all and is being trained by Gokou. Gohan has married Videl and they have a daughter named Pan.