Idk if i juat missed it but whos gabriel? The one theo was writing to at the beginning of ...

gabriel is cedric ,theo thinks what they do and what he has done is sin(killing of innocent kids leaving his brother to his sick father was selfishness) he think cedric as god's angel so he is confessing his sins through letter in the beginning and by the end of manhwa cedric read them and burn them.-hope that clears

Oh ok. Thanks!