Spoiler
He killed mc's dog and mc got so mad he followed the big bro why he did that on the stairs and accidentally fell after big bro accidentally push him.
As we know, mc lost his eye.
That time, the mother is so mad she almost throw a chair i think at big bro. But mc stopped the mom and said he fell by himself and don't hurt big bro or smthg. That time, the big bro realised mc is weak around weak things and capable of affection and wanted that affection for himself (not accurate since i use ggl translate to read lol)
Big bro became so obsessed and kinda lead mc to think that the big bro already killed almost everyone mc knows in the outside including ml and threatened to kill more if mc refused him
you didn’t want him to cling to you, now you do everything to cage him to your side lmao