What was the original piece if this was a doujinshi ?
It doesn't, because it is the original one. If I remember correctly, this is just a one shot from a collection of short stories sensei made in the earlier years. Doujinshi isn't always derived from an original/existing work and can just mean it's something authors produce independently on their own. Hope this helps!
The author just revive them for the sake of them existing. They just want the characters to be there, like, to capm down the audiences that “there, your favorite characters are alive again” and they completely erase what makes them (the character) them. The scars and mistakes are what forms a human and they just absolutely discard it. Hwan doesn’t truly loves Chiwoo, he just love his outter shell. His soul, his memories, his character is of another person but Hwan doesn’t feel anything. On the other hand, Chiwoo realized the fake Hwan and doesn’t like him or the fake family that Hwan make for him. This book is absurd and have poor plot. It have potential but just to canon a couple, it tooks a lot more than just revive a corpse.
And as for Jin, Hwan doesn’t feel any guilt after killing him, as if a life is of no meaning to him, even if he’s just a “monster” that Hwan creates, but in the end, who’s truely a monster?
The first time with Chiwoo is dub-con, then when things goes downhill, it varies from dub-con to non-con, like, what? On the other hand, Jin respect Chiwoo’s consent, and I’m not talking about this to say that Jin is a better partner, just to show that love also need to come with respect. Be a human, be a decent human, Hwan literally goes around and says that he r4p3 because of love…please…that’s not how relationship works…