I understand and it's ok to feel that way because I was hurt as well. I still shipped Mafuyu and Uenoyama but I felt the pain that Mafuyu had, why he seemed to be staring off into space all the time. Seeing how long Yuuki and Mafuyu been friends and involved in each others life, and then turned lovers, how they depended on each other. I believe that yuuki needed mafuyu a little too stongly, needed his love which was given, you always see yuuki holding on to mafuyu, mafuyu was his driving life spirit and he really meant it when he said that he wouldn't be able to live without him. I really loved that ship too. Furthermore; I understand that Mafuyu hadn't been able to express himself, held all of his tumultuous feelings inside, and blamed himself for yuukis' death, I think if it didn't happen then it would've happened at a later time because our poor yuuki was missing something deep within himself, or maybe not. I just really wished that they could've made up before his death or that yuuki wasn't drinking that night and knew that mafuyu wanted him to live more than anything.
I'm happy Mafuyu and uenoyama found each other, that mafuyu was able to express himself through music; hopefully this relationship will be a more healthy relationship and not a desperate need for each other.
All in all, I love this manga, anime and I can't wait for more!
Ya'know, after watching the anime, specifically the episode where Mafuyu sings and it shows a flashback of Yuuki...i struggled to support MafuxUenoyama...the people i shipped since chapter one, the couple i would fangirl about every time they interacted. I had to rewatch that scene literally 30 times before it stopped feeling like my heart was being punched and i could finally go back to supporting my ship! The point is, i didn't expect the anime to throw me this curve ball family haha. And don't @ me talking about "iTs noT rEAl". My feelings are real, and they was hurt hahaha