i mean, it’s one thing if makoto loved his brother normally, but he’s like insane. he only talks about his brother. he shows up after all his classes. he’s a brocon, he’s practically in love with him. i’m sure if he cared for his brother like a normal sibling they wouldn’t try to separate them. mutsumi himself doesn’t even want his brother to be around that much, he knows it’s overkill. i don’t think the twins would try to separate them if their relationship was normal.
I don't think he's insane and I also don't believe he's remotely close to being "in love with him". I still have my parents, but I can imagine losing them and being responsible for my little brother, who is my ONLY family left, yeah I would be hella overprotective too. He's going overboard, but I think it's okay that he wants to protect his little brother from being taken advantage of by two older men? Did you forget that he was actually coerced into this job and that when he heard what it was really about, he wanted to refuse? But even if it didn't happen that way, Makoto has every right to be protective over Mutsumi, even if he did get into it out of his own free will from the start. Because his family is stepping into a job he knows nothing about, Makoto knows nothing about, so there's no telling if it could be dangerous in any way.
They can say that he's too overprotective and be right about that, but they never even tried to have a serious conversation with both brothers and talk about it. That means they are irresponsible, jumping to stupid conclusions and they're honestly being fucking childish. If there's a problem, you fix it with !!communication!! Not abusive behavior like isolating your loved one from the only family they have left.
mutsumi is an adult. your use of the words “older men” is kind of off putting because there isn’t a large age gap between them, it’s fairly normal. also i agree communication is a key that many manga characters don’t use. but again, mutsumi is an adult. he also believes his brother is being way too overprotective. it’s one thing if he was still in high school. or if he was still living under his roof and having to be taken care of, but this isn’t the case anymore. he’s smothering him, and the twins said that he is all makoto talks about. that’s weird, even by the standards of taking on a parental role. i think makoto still thinks of mutsumi as a kid, and he’s not anymore. you’re mad the twins are isolating his from his brother, that’s exactly what makoto wants to do to mutsumi! he wants to keep him from seeing two people he cares about! (which he has mentioned they are both important to him by this point, in this chapter) without listening to mutsumi’s feelings and opinions. so it looks like the twins are doing to makoto what he’s trying to do to mutsumi. i’m not saying that either of them are right, but only going off on the twins behavior without calling out his is a little hypocritical :/

also the brother + the twins ship, but I fucking hate how those twins want to keep the brothers apart. They only have each other left, it's plain ass abusive to try and separate them. Fuck them. They obviously don't deserve Makoto as they're literally doing the one thing that would make him upset, which is mess with his little brother. That's not love, fuuuuuck them.