The one where the male protagonist was a child being experienced on in a facility, his "hyung" wore a bird mask, a top awakened rescued and adopted him, he dies, goes back into the past, rescues a group of school kids with abilities, trains them, rescues and adopts his younger self, etc etc
The one where the male protagonist was a child being experienced on in a facility, his "hyung" wore a bird mask, a top awakened rescued and adopted him, he dies, goes back into the past, rescues a group of school kids with abilities, trains them, rescues and adopts his younger self, etc etc