Storification of Herms's Live Tweets
By channeling ki from everyone around him to create an energy sword, Trunks splits Zamasu in two. Even in this state, Zamasu continues to rant for a short while, before finally dissolving away. Goku congratulates Trunks on a job well done, comparing his sword to the Genki-Dama, and Bulma and Mai arrive with the time machine to thank him too. Trunks says he couldn’t have done it without everyone’s support.
However, suddenly the sky fills with dark clouds showing countless copies of Zamasu’s face. Though he has lost his physical body, he still survives in a strange, gas-like form. Gowasu speculates that Zamasu is now trying to merge with the universe itself. Goku and Vegeta try to become Super Saiyan Blue, but find they no longer have enough energy after using the Final Kamehameha as Vegetto. Regardless, they fire blasts at the Zamasu clouds in their regular states, and Super Saiyan Trunks chips in too.
However, none of their attacks have any effect on the Zamasu clouds, which soon cover the entire Earth and begin raining down blasts of energy on people worldwide. Goku and co. shield Bulma, Mai, and the time machine, but around the world Sea Turtle, Android No.8, and everyone else get wiped out. Back in the present, kid Trunks and the rest at Capsule Corporation see Zamasu’s laughing face in the sky, and Whis and Beerus can tell something’s wrong off on their own world. Zamasu is somehow affecting the present, like when Goku Black attacked with the Time Ring earlier.
When the smoke clears, Trunks can’t sense anyone else’s ki. They’re now the only survivors on Earth! Though their attacks don’t work on Zamasu, Goku refuses to give up, and roots around in his pocket for one more Senzu. There he finds the button the Omni-King gave him! Goku asks Kaioshin if Omni-King would even still be around in this future. Kaioshin thinks so; after all, nobody could ever defeat him! Goku presses the button, and Omni-King instantly appears.
However, this is the Omni-King of Trunks’ alternate timeline, and has never met Goku. He asks who Goku is, where he is, and why the place seems to be such a wreck. Omni-King finds the laughing Zamasu faces in the sky annoying, and when Goku suggests he wipe them out, Omni-King instead decides to destroy the entire world!
Goku tells everyone to escape in the time machine, while Kaioshin and Gowasu use their Time Rings to flee. Everyone safely manages to return to the present, where future Mai meets her past self and kid Trunks. Beerus and Whis come over too, and Beerus tells Gowasu to pick a better pupil next time.
Though Trunks and Mai’s entire future world has been destroyed, Goku has one idea: he and Trunks use the time machine to head back and pick up Omni-King in the future (who’s now floating amid nothingness). Back in the present, Goku next has Kaioshin take them to present Omni-King’s palace. Now Omni-King has his own future self to play with! This idea impresses the Great Priest (who it turns out is Whis’ father), who decides he’ll come visit Universe 7 sometime.
That night at Capsule Corporation, Whis has a plan for how Trunks and Mai can return to (a version of) their timeline. It involves creating yet another alternate timeline, an idea Beerus doesn’t like, but Whis points out that Beerus already created a new Time Ring and timeline when he destroyed Zamasu, so he can hardly complain.
Whis’ plan now is to travel to Trunks’ timeline before Beerus and Kaioshin died, ask Beerus to beat Zamasu, then seal the defeated Zamasu away, Mafuba-style (Whis reveals that he has something much better for this than the jar Goku was going to use). This way, they’ll create a new timeline where nobody got killed by Zamasu. However, there would already be versions of Trunks and Mai in this world, which could be awkward if the Trunks and Mai here went to live there. But Mai is fine with this, since she’ll be able to live with all the friends she fought alongside with.
Beerus decides to let Trunks off the hook for his time-travelling shenanigans, and departs with Whis. In Universe 10, Gowasu puts the Time Rings away, reflecting that this affair was his sin. The next day, everyone sees Trunks and Mai off as they use the time machine to head for their new home. Bulma jokes that her future self will have grandkids before her, Goku assures Trunks he’ll be more than a match for any new threats that might emerge, and Vegeta briefly spars with his son.
As Trunks and Mai take off, Gohan and Piccolo fly up to wish them farewell, and Trunks gets emotional thinking about his old mentor. Trunks thinks that he’ll meet them all again someday, and the time machine vanishes.