I think the pink haired guy died in an accident in 2008 and the only way for him to cope with it is to imagine him, the black haired guy must know about it. But there had to be an accident afterwords for him to forget. May it be to traumatic.
But in chapter 1, MC pulls out a picture with both of them in it and it's dated 2017 so maybe it happened more recently
Yea that makes sense, I definitely feel like the pink haired guy is dead though
I think he's imagining Sihoo there in that photo... [he only thinks he sees Sihoo]
Everything so far points to that being the case...
-The photo album having no pictures after 2008
-Myunghan saying to Seungchan that he hasn't been on a trip anywhere for the summer break since preschool [the last time he was away, at the beach; the last time Sihoo was alive]
- The flashbacks of him in the hospital, and then of other kids telling him "aren't you going to the hospital" , "I feel bad for him" [he's depicted as a kid when this happens...] [chapter 4, page 22]
- The flashbacks of him as a kid, being bullied for having "monster eyes" and him saying to his bullies "But I'm telling the truth" [chapter 5, page 36]
-Lastly, he says to himself at some point, "why me? Why does this always happen to me?" Which implies his situation has evening going on for a while
Hope this helps... *runs back into the anonymity of the internet*
The painting he bought is actually hers