They're all fucked up.
But like from a regular point of view, if I found out my best friend was hanging out with my stalker I'd feel betrayed too. Like imagine if someone tells you their your friend while actively also being friends with your abuser/stalker. So it's pretty normal for Mitsu to be pissed off and Tate should feel guilty for being friendly with someone who is actively harassing his best friend.
I mean I don’t think black hair guy abused Blondie?? Also kinda annoying how he went in and did that, sure he’s annoyed but it’s still not his place/ house and it’s short hair guys decision nonetheless. Plus Blondie is using black hair guys feelings for him, and using short hair guys feelings towards black hair guy so idk I feel Blondie is kinda being a bit manipulative lol, (yea that’s probably why I lowk can’t stand Blondie) black hair guy is alr pretty beat up from all the circumstances it seems
No I mean in general if someone abused or hurt you or stalked you then you would feel betrayed and upset if your bestfriend defended them. Black hair guy also had no right to take pictures of Mitsu and follow him anywhere, even go as far as moving right across and take pictures of the apartment, also posting threats to tates door etc. Those are all crimes. How is Mitsu using tates feelings? It's the other way around, Tate pretended to kiss Mitsu and is using Mitsu to get closer to black hair. He even says directly that he is aware of mitsus feelings but still uses him to make black hair jealous and interact with him. Tate was just pretending the whole time to protect his best friend from his stalker but actually used his bf to get closer to the stalker. That's just as fucked up. Also him doing a background check on black haired guy is also an invasion of privacy. None of them are innocent.

Blondie pisses me the fuck off. Not only did he kiss tate while he was asleep, now he does it again without his consent and motherfucker walks into his room like he owns the place and kicks stalker out like who do you think you are ?? Tate can keep the guy with him if he wants blondie's not the boss of him istg he's so full of himself does he think tate belongs to him or smthing ??