Goku and Vegeta's training with Whis and Beerus is interrupted by the arrival of Future Mai, who tells them that Future Trunks has been captured. A mysterious figure emerges, introducing himself as Fu; he tells Goku, Vegeta and Mai that Future Trunks is trapped on a world called the "Prison Planet", a planet where warriors from alternate timelines and dimensions fight as part of an experiment conducted by Fu. The trio arrive on the planet and meet an alternate version of Goku, who is revealed to be part of a group called the Time Patrol. This Goku, referred to as "Xeno Goku", sees Fu and assumes that the trio are working for him; he immediately transforms into Super Saiyan 4 and attacks Goku, who reacts by transforming into Super Saiyan Blue. During the fight, Goku discovers that there is an invisible barrier around the Prison Planet that prevents them from escaping. The two Gokus engage in a Kamehameha clash, but their blasts cancel each other out. Fu deduces that Xeno Goku was trying to use the combined Kamehameha waves to break through the barrier, and explains that the Prison Planet is inescapable unless the group searches for a set of Dragon Balls (one of which is in Xeno Goku's possession) that they can use to escape. Fu disappears, and the two Gokus agree to work with each other to escape the planet. Meanwhile, Future Trunks is in a prison cell elsewhere on the planet. After escaping his cell, Future Trunks is confronted by Cooler, who demands a Dragon Ball from him. As Fu observes the planet, he tells a seemingly evil Saiyan that his time will come.

The evil Saiyan escapes his prison cell and attacks Goku, Vegeta and Future Mai. Goku and Vegeta attack the evil Saiyan, but his aura drives Goku berserk, causing him to attack Vegeta. Fu reveals that the evil Saiyan's name is "Cunber", and explains that his energy can turn people into a berserk state by just touching his aura. Goku continues attacking Vegeta; Future Mai is almost caught in the crossfire, but Future Trunks appears and saves her. Vegeta orders Future Trunks to fight Goku while he goes to battle Cunber, but he's interrupted by Cooler, who now appears to be working with Future Trunks. Cooler begins fighting Goku and transforms into his own Golden form, which he calls "Golden Cooler". Using this form, he defeats Goku, snapping him out of his berserk state and returning him to normal. Cooler then launches a Supernova attack at Cunber, but the evil Saiyan survives unscathed, breaks free of his restraints, and attacks the group once again. Future Mai reveals that the Supreme Kai gave her his Potara earrings before they left Beerus' world, and gives them to Goku and Vegeta. Future Trunks and Cooler distract Cunber, who easily defeats Future Trunks; however, this gives Goku and Vegeta enough time to fuse into Vegito. Vegito powers up to Super Saiyan Blue and prepares to fight Cunber.

Just before Cunber can kill Future Trunks, Vegito transforms into Super Saiyan Blue and saves Future Trunks from the blast. When Cunber weakens Vegito, he transforms into Super Saiyan Blue Kaio-ken x20 and continues to fight Cunber while Cooler observes, noticing that the chains around the Prison Planet have begun to break due to Vegito and Cunber's fight. As Cunber prepares to fire a ki blast, Vegito attempts to counter it with a Final Kamehameha but fails. Cunber then creates a full moon to transform into a Golden Great Ape. In this transformation, Cunber attacks Vegito which prompts them to defuse back into Goku and Vegeta. Goku and Vegeta then prepare to battle Cunber one last time.

Having defused back into Goku and Vegeta, Goku suggests cutting off Cunber's tail to revert him back to normal. As Cunber fires yet another blast at the Saiyan pair, Goku and Vegeta avoid it and fly directly upward, transforming into Super Saiyan in the process and attempt to get to Cunber's tail but even at his great size he proves to be swift enough to defend himself. As he steps on Goku, Future Trunks rushes in to help and tries to cut off the Golden Great Ape's tail with his sword but is struck hard to the ground. Along with his father, they fire a volley of blasts though they do no damage to him. Even when Golden Cooler fires blasts of his own, Cunber is still unfazed. Meanwhile, Fu continues to watch the battle from his laboratory, smitten by the current events when a nearby computer informs him of the damage to the Prison Planet's barrier and decides to go to the battle himself to control matters. Goku still remains under the foot of Cunber, struggling to get free but is them seemingly crushed. However, Goku transforms into a Super Saiyan Blue and throws Cunber's foot off of him. Charging directly towards Cunber, Goku uses the Super Saiyan Blue Kaio-ken x20 and strikes Cunber in the face though he is unmoved. Goku fires a Kamehameha though the move is blocked. The ongoing battle causes the barrier to break down even more when suddenly Fu arrives, telling Cunber to watch what he's doing as he declares that he will rein him in. Fu powers up into an empowered state and gathering the energy from the Power Ball to his sword, he strikes at Cunber which causes him to revert to his normal state. Cunber throws a punch at Fu but he easily avoids it. While the others comment on what he just did, Fu tells them to continue their battle as he teleports away, avoiding Cooler's blast in the process. Cunber powers up once more and Goku vows to take him on as he transforms into a Super Saiyan God as Cunber appears to recognize it.

Cunber and Goku's battle breaks the seal around the Prison Planet, while Fu is enraged to discover that his laboratory has been destroyed. Cunber defeats Super Saiyan God Goku and knocks him unconscious. Just before Cunber can kill Goku, Xeno Goku and Xeno Vegeta arrive as Super Saiyan 4s and save Goku. They challenge Cunber, who transforms into a Super Saiyan, so Xeno Vegeta suggests that he and Xeno Goku use Potara fusion. They put on the earrings and fuse into Xeno Vegito. Xeno Vegito battles Cunber and manages to subdue him using a Kamehameha, before separating back into Xeno Goku and Xeno Vegeta. The resulting explosion breaks the seal completely. Fu returns, now furious over the destruction of his lab, and attacks Xeno Goku and Xeno Vegeta, who manage to block the attack. They then charge at Fu.