My opinion

So, I want to go over some reasons people mention when they try to take Mafuyu down.
*Mafuyu is responsible for Yuki’s death.
Well, No! That’s wrong. As someone who was suicidal in the past, you should have reached the real dead end to want to take away your life. You should have a great reason, you should be really tired and pressured to commit suicide. It’s not like someone tells you “die” you say “ok”. Same goes for Yuki. He wasn’t fine, he was already dealing with stuff, it can be anything, but his reason for killing himself wasn’t that fight, and I think that’s what the author is trying to portrait, that even though Mafuyu’s words weren’t the cause of Yuki’s suicide, but Mafuyu himself can’t get over the thought that he IS responsible for that incident. I’m not saying their argument wasn’t a push for Yuki but I’m saying Yuki was already there, he needed help and he didn’t get the proper help he needed. (Same goes for Ugestu, he really does need help!) I get Mafuyu blaming himself cuz at the end he lost a loved one, but for readers who are looking from outside, blaming him is just unreasonable.
*Mafuyu is using Uenoyama as a replacement.
No! Mafuyu is hurt, he’s broken, and he needs help to recover, and that help is coming from Uenoyama. Of course, he still thinks about Yuki, some of Uenoyama’s behaviors and actions remind him of Yuki, but that doesn’t mean he’s using him as yuki’s replacement! Mafuyu needs to move on, you don’t want him to cry forever or kill himself, too, right? This is life, we lose loved ones and if we don’t move on, we can’t live. I don’t mean forget people who pass away, no, but learn to live with reality and try to find happiness in other ways or with someone else.
*Mafuyu was not loyal to yuki.
You can’t wear black forever, there needs to be an end. Mafuyu was drowned in sadness, negative feelings, guilt, etc. He moved on not because he wasn’t loyal to Yuki but because as a human that’s what he needs. We all experience losses, family members, friends, bfs/gfs,… what do we do? Cry for a while, wear black, deal with depression, but don’t we also try to move on at some point? We do, we should.

Don’t get me wrong, I love Yuki. He was selfish for taking away his life and leaving everyone else in misery, but who am I to judge when I was in the same boat as him? He was a human and he was tired, and everyone has different limits. I love him and I adore him, but he’s gone, and everyone needs to understand this. If you see the same situation irl, don’t blame people like Mafuyu, don’t judge them, don’t break them more, if you can’t understand them just don’t give any comments. The story is showing slow development, it shows that people can’t move on quickly, but it takes a long time, just like Mafuyu and Uenoyama’s relationship. Mafuyu is opening to him slowly and Uenoyama is also understanding him more, slowly. So, try to love all characters instead of spreading hate.
(づ￣ ³￣)づ