After the explosion of the cleaning machine, the young demon's negative energy causes him to transform into Janemba, a powerful monster with reality-warping abilities. Janemba proceeds to wreak havoc in the Other World, creating portals that allow deceased villains to escape and cause chaos.
Goku and Vegeta separately attempt to defeat Janemba but are unable to even hurt him. They eventually realize that their only chance of defeating Janemba is through fusion. Vegeta reluctantly agrees to fuse with Goku, creating the powerful warrior Gogeta.
Gogeta manages to overpower Janemba with ease, but the monster is able to reform himself the moment he is destroyed. Gogeta realizes that Janemba is being controlled by a weaker demon named Saike, who is only able to maintain the monstrous form through the energy Janemba is expending.
After defeating Saike, Gogeta is able to take down Janemba in his true form, reverting him back to the young demon. The young demon apologizes for causing so much trouble and offers to help clean up the destruction caused by Janemba's rampage.
