i don't know. when you have a chance to choose the best thing and even so you choose the worst, it makes you dumb af. are you kidding me? in stories like that in which someone is being manipulated there's an actual reason for them to believe the manipulator, but here??? are you fucking kidding me. the guy is a mess of bad choices. he made bad choices even when he wasn't being manipulated at all. dude was being beaten almost to death and it took the boyfriend to stop it??? if it was for him, he would just gladly accept death?? how does it not make a character dumb? would you accept all that from someone that rapes, beats and humiliates you every single day? and he's not even that kind of character that is shown as someone weak. if it was i wouldn't call him dumb, but the author didn't. he started the story with a character behaving in a way saying "enough is enough" (even if hesitant) and then he just became a brainless doll. the character is inconsistent and when is written like that, he just seems dumb.
Honestly I don't really care what you think, since this is a story with characters. I just hope that the both of you will choose a different reaction if you ever see a victim in real life. That you'll choice to try sympathise and understand them rather than be ignorant and think you're above them. The MC and deep rooted insecurities that were implanted in him from his ex-partner which were used against him. Its hard to stand up against an abuser, decisions aren't so simple in those situations, there's always more to it than just "choosing".
Do you think manipulation is all it takes to abusive relationships? Mitsuru was made to believe he wasn't worth of Shougo not only through manipulation but also by chipping away his sense of self taking advantage of his low self esteem and the fact that he was still seeing his ex as the man he loved for 5 FUCKING YEARS. So of course it never crossed his mind he would do something like what he did at that hotel. He still had that veil of the past. And then all the ex needs to do is confirm what he already thinks of himself. He's not enough. Everything is his fault. So he stays with his ex mostly as a punishment to himself. He can't go back to Shougo. He's unworthy of him. That's why he demands the ex to abuse him. Like you really sit in your supposedly elevated ground and impart judgement on a story you couldn't comprehend. Good job!

the mc is a whole new level of dumb