Your paragraph here, is tbh, completely sexist and in my personal opinion rather rigid. The MC shouldn't hit her because hitting people is bad. PERIOD. Not because she's a girl and he's a boy. That kind of view is rather narrow. So if the girl is as strong or stronger, is it suddenly fair game?
You're arguing from a perspective of "this is how society should be," but that utopia has yet to arrive and will likely never arrive.
I'm not sexist, society is. Is it a sexist belief that MC shouldn't hit her because she's a woman. Yes. Is that also the broader prescription that society teaches boys and considers to be noble and justified, even though it's a blatant double standard? Also yes. Has the conversation of "equal rights also means equal lefts, women can't pick and choose" done a good enough job of removing the taboo from the action of a man hitting a woman being seeing as antisocial and morally abhorrent? NO. Like I've said before, it's fun to dabble in ethics, but sometimes ethics/morality ends up being very incongruent with what is realistically possible in society.
Your reasoning is not at all applicable to the story or the situation this would fit in. Hitting a woman does not automatically make you anti social or a social outcast due to something called "context" and if you are willingly want to ignore the context of each situation and immidietly deemed that "guy hit girl, guy is bad" is at best ignorant and at worst can cause real damage.
Are you really telling me, that in a post MeToo Western world, that hitting a woman has no social consequences for a man, regarding his reputation? You talk about "context," as if it was an important thing the public at large takes into account when forming opinions on these situations, and yet if that was true, there wouldn't be such a huge public outcry against the notion that men are justified to hit women back if the latter hits the former first. Society will still largely prescribe the sentiment of "men shouldn't hit women back, even if they're hit first, rather they should try to de-escalate the situation." An overwhelming majority of women and a considerable majority of men still believe that men shouldn't lay their hands on a woman, ever. If you have any doubt, go and look up the number of cases where the woman was the physical aggressor against a man in public, yet no one comes to his aid, and yet the second he tries to justifiably defend himself, multiple men jump the guy for "hitting a woman."
This shit happens all the time and why men try their absolute best to move away from the violent women rather than try to square up and defend themselves outright, because they understand intuitively that society will likely stand by a woman who was hit by a man, regardless of context. Men simply don't make for sympathetic victims the way that women do and ignoring this reality is naive. Literally every man knows this. I want to ask if you're a man or a woman? There is no way you don't intuitively understand what I'm saying if you are indeed a man.
And the examples you provide doesn't at one bit applicable to this story at all. The MC does NOT care about searching for any romantic partners all he wanted is to seek the justice that was unfairly taken away from him. Who cares if the girls got an ick from it, he probably doesn't even want to interact with them.
I also talked about the prospect of losing social connections/friendships, the lack of which would serve to alienate and make a man a social outcast, not just romantic prospects.
And in the real world. Again, CONTEXT. If the person you're interested is the type to already make up a story in their mind about something that they have no clue about and develop an "ick" then good, cause that ain't the person you would want to be with anyway regardless of gender.
You severely underestimate the extent to which our cogntive biases, influenced by our own values, rule decision-making and opinion-forming processes of human beings. You say as if the person who's interested in making up a story in their mind based off of limited context/evidence is in any way rare, or even a minority, in society. Just think about how many people jump to conclusions about sexual assault/domestic abuse cases that are come into light online going off of the initial wave of limited context. They don't even wait for the court proceedings to begin, they outright socially execute the accused in the square of public opinion, which has now extended into the online sphere thanks to social media.
Also, practically every measure/findings of how our cognitive biases influence our thought processes goes to show how ridicuously biased human beings are - so much so that we should basically retire the colloquial use of the word "rational" as it applies to human beings. Human being are not rational. There is no single part of the brain that gives rise to the "rational" function in humans. All of our thought processes are heavily influenced by our values, cognitive biases, the heuristics we assign to the events we observe, and emotions. Given all of this, it is super naive to think you can easily find people who even acknowledge their own biases, let alone take the extra step to controlling them (the latter of which I don't really think is possible for human beings in general anyway, judging from the literature I've read on neuroscience).
You are able to make the correct guesses and have the right opinions about Kokonoe's situation because we literally see his POV and know that, as the MC, he is being thrust into an arc whereby he is unjustifiably bullied due to a wrong he did not commit. It is much, much more difficult to make such objective assessments when you're not a reader, but actively involved in the situation where all of a sudden, your shoes are stolen and dumped in the nearby pond even though you did nothing to physically bully Kokonoe on your own (even though others did bully him and all you did was be a bystander - which is bad, but not as bad as the bullies themselves).
The Question here is not whether he was in the right. He was. He did however took it further than needed, both with the boys and the girl. And the girl isn't some innocent bystander. So according to you, she should just be able to get of w a slap on the wrist. Don't they deserve to receive the consequences for their actions? She see a kid getting gang up and her reaction is "Yeah beat him up some more". Is that kind of behavior not in itself anti social?
I actually think he didn't take it further than it was necessary against the boys who were being violent towards him at all. He was outmatched and had to quickly subdue each one before they ended up landing any potentially fatal or life-altering strikes (last chapter showed one kid curb-stomping his head into the ground, which considering his age, could spell either death or being put into a vegetative state in the hospital), so he fought them off individually, as well as inflicting enough pain/fear to ensure that the bullies do not take another retaliatory action of violence against him in the future (which to me is an underrated part of self-defense, since victims who often stand up to their bullies simply suffer more violence in the future in unjustified retaliation).
I did however think he took it too far with the girl. All he needed to do was glare at her and use some threatening words like he did to make her cry out of fear and all but piss her pants. She got the message, she knows what she wil be risking if she tries to incite more violence against Kokonoe in the future. He took it too far by actually trying to hit her, because at that point, the immediate threat of violence was dealt with, as well as making sure he took actions to discourage any future events of violence against him. At that point, hitting her would only serve as a way for him to satisfy his desire for revenge and quelling his anger, neither of which are morally justifiable reasons for using violence, since once again, the threat against him is gone.
And yes, the girl's action of cheering on violence is indeed anti-social. Does that mean that she deserves to have Kokonoe knock the daylights out of her face with his full might like he was going to? What punishment do you think is justified for her? I simply think that a talking-to, getting in trouble with the school leadership, as well as potential suspension from school for cheering on unjustifed violence (which is both immoral and illegal) is either a good starting point or is enough by itself. Tell me what you think she deserves. I want to know where you're coming from in terms of your moral framework of justified versus unjustified violence.
In the end, you're entitled to your opinion. And all the more respect that you can turn the other cheeks. But thats YOUR opinion, your moral standards. And that doesn't apply to everyone, especially since it actively is sexist and hypocritical.
Yes, I am entitled to my opinion, as are you. But this isn't just my opinion, it is the LITERAL status-quo of society. Only one of our opinions actually maps onto reality, and it isn't yours. Yes, society is sexist and this does indeed apply to everyone (insofar as the exceptions can be considered a negligible minority, powerless to affect status-quo). The utopia you want of absolute gender equality/fairness will never arrive, because it will involve taking away patriarchal privileges/protections women have always enjoyed, and since women make for sympathetic victims due to their comparative fragility/vulnerability, unlike men, you will NEVER convince society as a whole that making it similarly okay for a man to hit a woman (like it is for a woman to hit a man) is a noble cause worthy of societal change/pursuit. It simply won't happen. It isn't based in reality, but an ideal world that will never arrive.