briefly touched on him in a twitter post but i want to talk about him and my theories a bit more indepth!
getting right into it! i believe he may have some struggles with figures of authority. he seems to have quite a stable relationship with umemiya and the rest of the four kings (especially momose, it appears, as evidenced by their interactions in ch190. i'm exicted to see if they have any further history together!) and he seems to be able to respect furin as a whole.
his main problem seems to lie with sakura's position.
it's already clear he has a very standoff-ish demeanor when it comes to sakura. he's straight off the bat in his face and fighting him, disrespecting his position in furin.
due to him and sakura being in a (presumably) similar age range, perhaps momijikawa could've had previous trouble with older children in school. he emphasises feeling like he should be allowed to do whatever he wants. perhaps he could've had issues with being bullied by these older children, like he was being controlled and bossed around by them.
i believe some of his trouble may also lie in sakura's attitude.
when sakura came to furin initially, he was quite similar to momijikawa. didn't believe he needed anybody. thought he could be alone and there'd be no issue. "when he's so strong, why should he bother with other people?". that sort of mindset.
i believe momijikawa may have seen this way of thinking and initially may have respected sakura. like they could've found common ground, but once sakura's attitude began switching from an independent mindset to a more allowing-himself-to-be-dependent-on-others mindset, he began to view sakura differently.
it's already known that momijikawa has a reputation for being a lone wolf. that he doesn't work with anybody else. he's looked up to for being independent and strong.
perhaps he now thinks that sakura is weaker because he has let others around him. that letting himself get all chummy with other people is going to make him weaker.
part of it could be pressure to keep up his "lone wolf" appearance, but it could also be...
"he doesn't even know what team work is."
this line really stuck out to me. could it be that momijikawa is jealous of sakura's development? sakura struggled with teamwork and relying on others too. could it be that he's seen sakura change and grow and become jealous, and that jealousy has turned into anger towards him? could it be that due to possibly negative experiences in the past, he was never able to figure out teamwork, and he loathes sakura because he can work in a team?
of course, these are all just thoughts i came up with on a whim. who knows what nii sensei actually has in store for us! definitely excited to see how this develops
