Kei is in the back of a Toyota Harrier with Urachi, with Tsushima driving and Tomoki riding shotgun; Ukawa, Murase, Sakagami and Oka Eri (I’ll say her whole name since everyone in the show always does) escape by bike (and Ukawa turning the road into a slot car track). Haruki is still at the Karaoke parlor with Sakuin and Kagaya, apparently outnumbered…but it’s all part of the plan.
I hope you don’t mind the calm, measured voice of Ishikawa Kaito, because you get a lot of it in this episode, and that’s saying something. He has an adversary with the opposite position to try to convince to his side, after all.
Kei is as persistent as he is righteous, laying out all of the alternative options to simply wiping out abilities, using the abilities of others to lighten the burden of his two “locked” parents—even transferring his father’s ability to a cat.
At the end of Kei’s spiel, Urachi is still not convinced, and Kei isn’t surprised…because Urachi isn’t the one he was trying to convince: it’s Kagaya, back at the parlor with Haruki, who heard the whole debate through Tomoki.
In light of everything that was said, Kagaya chooses to support Kei. Just like that, Urachi loses a vital team member of his crusade. He can no longer realistically carry out his plan without Kagaya’s support, so he essentially surrenders to Kei, handing him his notebook.
As for what occurs at the very end, with Souma passing thorough the boundaries of Sakurada in a train, suddenly having all her memories rush back, and lamenting that she’s “certain nothing was even” for Kei? Your guess is as good as mine. It would seem Urachi has been quite suddenly removed as an opponent, but perhaps the events of this episode were the easy part of Kei’s plan, with the true challenge coming in the finale.