After of S2: following the destruction of Slate and the death of the Green King, Adolf K. Weissmann takes Sukuna Gojo under his wing. After some time, Sukuna even begins assisting the Silver King in scientific research. (Imagine that Adolf doesn't become a teacher but continues his scientific endeavors, with the members of his clan assisting him. This also means that they don't live in the school but, for example, could move to Mihashira Tower.) This also means that Kuro and Yukari will see each other much more often.
This would be an interesting direction for Sukuna, I feel like he would be resistant to having anything to do with the Silver King because he can’t help but hold a grudge about Hisui. Maybe it’s partly a way for him to avoid his parents, like imagine post-ROK Shiro has decided to continue his scientific research and kinda shares time between Mihashira and Ashinaka (I think he would want to keep his room at Ashinaka, and he’d want Neko at least to go to school). One day Yukari shows up at the tower with an irritated Sukuna in tow. Kuroh is immediately suspicious and Yukari is being all friendly to him anyway, stating that they aren’t enemies now. He admits that he does have an ulterior motive and explains that Sukuna met with his mom on the street and now she’s using all her wealth to try and track him down. This is dangerous for both of them, since Yukari himself is technically a criminal, and he’s concerned for Sukuna’s welfare should he end up being sent back to his parents. Sukuna claims that he doesn’t need any help and especially not from the Silver clan, and Kuroh gives him a disapproving look because clearly Yukari is trying to look out for the kid here and that’s admirable.
Ultimately they decide to let Sukuna stay in Mihashira for a while, where he won’t be found by even a private detective. Shiro has a bunch of games brought in for him but Sukuna gets bored of them quickly because they’re all too easy (and he won’t admit it but he misses Yukari, who stops by to visit him often but also goes off to do his own thing most days). He ends up wandering into one of the research rooms where Shiro is working, Shiro asks if Sukuna likes science. Sukuna shrugs and says he isn’t interested in learned boring things, Shiro’s like ‘I see’ and goes back to his research. Sukuna watches for a while and finally gets antsy enough to ask what Shiro’s doing. Soon he’s listening with interest as Shiro explains his work.
It turns out Shiro really likes having someone else who’s interested in this kind of thing (Kuroh isn’t much for science and Neko complains that it’s boring) so Shiro ends up taking Sukuna under his wing a little. I could see Sukuna feeling conflicted about this, since these guys did kill Nagare, but Yukari reminds him that they have to live in this current world and can’t hold grudges forever. Yukari himself has been spending more time at Mihashira too, not just checking up on Sukuna but catching up regularly with Kuroh. Maybe Shiro even decides to help with this, he convinces Munakata to take Yukari and Sukuna both off the wanted list and to have Sukuna’s guardianship transferred over to Shiro so that Sukuna’s parents can’t touch him. Yukari is grateful for this for Sukuna’s sake at least and tells Kuroh that it seems he’s found a good King after all. Kuroh was initially wary of both Sukuna and Yukari spending so much time with his King but he’s starting to enjoy this as well, like he and Yukari are able to mend their fences and it feels like they’ve all finally entered into a time of peace.
