That wasn't forcing, manipulation or rape. Both of them are fully grown adults, close in age and on top of everything, they're friends. If the uke guy really wasn't interested, he could've rejected more firmly, without any consequences. He wasn't anymore a victim than I would be if after refusing my friends' offer to go out drinking, I decide to go out any way, because they were being really insistent, and then got drunk out of my wits. I can't make them out to be a villain simply because they didn't give up after I said no the first time. Because in the end, going out to drink was my choice and my choice alone since they had no power over me. They are just my friends. I could've just not gone no matter how much they whined and nothing would've changed even if I done so. It would've been different if it was a superior in my company being this stubborn, though. Because now there is a power gradient involved. That will be considered manipulation because there is a risk to me if I refuse. I will be forced to consider what I stand to lose if I refuse. See, it is a threat and manipulation only when a reasonable sense of fear is involved, and not when you decide to go along with your buddies' antics just because. So, that's my take on the moral question here that's actually significant.
On to the more frivolous issue that is sexual infidelity or breaking up, moving on with new person when it comes to sexual relationships in general, I don't give a shit, personally. Sexual relationships, or "romantic" relationships as you people like to call them in polite company, are the most insignificant human relationships, in general. Why should sexual associations be able to demand a favoured priority or exclusivity when even your most fundamental relationships don't demand it? A child can't demand to be your only child, a parent doesn't demand to be your only parent, a sibling doesn't demand to be your only sibling nor does a friend demand to be your only friend. And yet, these are the people who you love and who love you, more unconditionally than anyone else. No personal relationship, other than a sexual one, imposes on you to ditch everyone else in your life and only cater to it. Given how trivial a romantic or sexual relationship is, by its very nature, compared to all other personal relationships, it is disgusting how much value, time and effort, people are forced to put into it all because of social expectations. A lot of time, effort and thought that should rightfully go into far more important relationships.
Sleep away with whoever you want, as many you want, as long you don't let your sexual associations impact your family, as in, your kids, your parents and your siblings. The interest of those people are non-negotiable. But if you want to go even further and be a nicer person, honour the bro code. Bros before hoes, pals before gals, and sisters before misters, has been a time honoured lesson that far too many only realise far too late in life. To summarise, I don't really care about betrayal, heart break or whatever overblown emo drama people like to indulge in over "romantic" associations dissolving. I don't really judge people over it, either; neither in real life nor in fiction.
But you are different, you clearly do care. So, here what we'll examine is your own moral standards, or rather, your enforcement of it with respect to the two "love" rival characters in this story. You condemn Chika for going ahead and marrying as per his family's wishes. Which should have been a no-brainer even if he been dating the uke at the time. In my opinion, that Chika guy makes the right decision in the end, even if he does it for the wrong reasons. He does the right thing by choosing his family's interests instead of thinking with his dick like you people would've liked him to. If he's already comfortable with sexual interactions, he's in a position privileged enough that he won't be taken advantage of no matter who his marriage partner is, and forming a strategic marriage alliance will benefit his family and make his parents happy, of course, he should marry. He should've married regardless of who he was dating. I don't get what the problem is, then, given that they have broken up already, apparently. That's what the comments tell me, I haven't read myself. Story was too cringe for me to last that far into the story.
But, given you are still this harsh on Chika for, I don't even know, not taking up an oath of celibacy pining for his ex-boyfriend, I guess, I don't understand then why you are so kind to the other guy, Masato, when the dude is thinking of cheating on his wife. Surely, in the priority ladder of sexual relationships, a wife, especially a wife that you are raising a child with, comes above a boyfriend or rather, an ex-boyfriend who is into someone else. He's a piece of shit, even from my moral perspective. Because, he has a kid, and clearly this isn't going to be the kind of story that'll end with him being responsible enough to just fuck the uke on the side while leaving his family intact, protecting them from whatever impact his indulgence will create, and making sure that his obsession with his trivial affair doesn't take his priority away from the one person who deserves it the most, his child. If bro had that healthy of a personality, he probably wouldn't even qualify to be the ML in a shoujo, let alone in a yaoi. He would've been the guardian/the teacher archetype in a shounen.
Shouldn't someone with your sense of morality, if they were been honest, hate Masato for committing infidelity against his spouse? Isn't it clear that you aren't disappointed, out of whatever sense of morality you have, but simply because you tend to have a protagonist-centric emotional investment when reading a story, and you just want the protagonist to get whatever he/she wants, every other character be damned. It's fine if you do. But, you should be cognizant of it. Don't take out your frustration on other readers for liking a character that you don't like and accusing them of liking "bad" characters, when you are the one who is reading the story from a biased perspective in the first place. You are the one who hasn't been reading the story, properly. The uke guy is just your baby and so, you just dislike any character against whom the uke shows any kind of negative feelings.
To all these people "siding" with Chika, did you even read the manga?
First of all, Chika manipulates Hotaka into this whole deal. She knows Hotaka won't fight him so he pushes for a bit more each time. And Hotaka obliges. Up until he's asked to say 'I love you' back, which is something he can't do. He could he? He doesn't feel that. Can someone in their right mind criticize him for that? No, I think not. It is stablished and reminded during the whole story three certain things. Hotaka gives way too much, but has a limit. Masato has strong romantic feelings for Hotaka and Chika, while pushy as hell when Hotaka is involved, will not go against his family. And those are the three things that make the story into what it is. Hotaka says yes every time to Chika because there's and end to the whole relationship thing. Chika has an expiration date (in the beginning Hotaka thought he would lose interest, but then it was actually because of his obligations to his family, which Chika would never leave, not even for Hotaka).
I feel like a lot of the people feeling sorry for Chika, would go to another manga and cry rape at another couple who does the same as Chika if not even less.
Masato is a high contrast to Chika. He takes time. Gives Hotaka space, takes care of him. He never takes advantage of him. And this is shown throughout the manga, so to say that he takes advantage of the break up can only be because you haven't been paying attention. He goes after Hotaka because he's worried for him. Nothing else. Yes, he confesses, but because of how things were going. He didn't go there with that express thought. That would have been a Chika move, and the author went to great lengths to differentiate both. So take your time, and fucking read