I think the bottom(can't remember the names) forced the red string in his past life and try to change fate, that's why all this misfortune happens to him in this life. There was a chapter mentioned that it's possible to forcibly apply a red string tho there are consequences to it. Maybe in this life the top's red string was suppose to be with that girl
But didn’t the black hair dude tie the string to him first? I had the same theory as you, but the bottom didn’t initiate it (from what we were shown at least).
I do think what the characters are doing is terribly wrong but the way the author write the characters just feel so real and raw that you feel connected to them and sympathize them, the story direction let the readers be hopeful for the mc's situation, like how killing stalking is so popular is not because of the abuse but suspense and curiosity of the readers , sure they could've write something without the abuse but that wouldn't make the characters feel real. If anyone thinks otherwise that's fine, this is just my opinion ╮(￣▽￣)╭
I got this theory that he actually poisoned his parents with spoiled food that's how they got sick for so long, and he's pretending to care about them in front of the top but he rlly acts genuinely towards his parents so im not sure and him pretending to be crazy this whole time means that he didn't care about his parents in the first place, I think the ending felt too rushed I wished we had the MC pov from the whole thing to just better understand the thought process and his plan