I have a lot, lol. Just 3 that I thought of first.
-If Genshin got back to Japan, when Kazuma got to university, he’d be overly doting on him in public, and it embarrasses him, but everyone just thinks he’s doing what dads do.
-If Kazuma ended up going to England, Barok and Klint would enable the hell out of Genshin, and they’d all spoil Kazuma, but Genshin would put a stop to Barok and Klint trying to take Kazuma’s attention away from him.
-If characters went as they did canonically, Kazuma would find out that Barok was in a relationship with Klint and Genshin, look at the pic of them Barok showed, and go “yeah I absolutely don’t blame you, you’re all hot” and when Barok questions Kazuma about his dad being there, Kazuma’s just like “did I fucking stutter”