Considering he had a previous life where he was a red/black flag, he has evolved a little to being a yellow flag with these senanigans.
He should have consulted Sejin first, ask if he agreed with the plans or at least warn him of what was to happen.
He probably did all this because he knew the family members where the ones who hurt Sejin in the other life and lead Sejin to end his life...
I dont like the top having a second chance with Sejin when he clearly doesnt deserve it, but I like how wicked and non green flag he is because green flags are not that common in the real world. Most people have several issues with their personality (even therapy cant solve everything) and I like how yellow/red flags have a much more realistic feel with insecurities, anxiety, manipulation... Things that happen in almost all relationships
If you have a problematic family member, DO SOMETHING.
Report them, send them to a mental hospital, send them to jail... Dont just wait for the worst to happen and/or hope for the best. Family members should be charged as accomplices for any felonies done by the family members. Its a shame this story is common irl, being assulted by someone you know and "trust". The ex-wife did the bare minimum to contain her brother, the parents failed to see what was so wrong with him and should definitely go to jail.
This is one of my favorite stories. Exposing how depression can seem to others like "happy/joyful" for the sake of not being seen as a "load". Denying the painful memories, erasing any physical evidence of it happening, does nothing but sink you deeper into the guilt, loneliness, shame, anxiety, anger, etc. How one traumatic event can and will spiral your mental state into insanity (squizophrenia, PTSD, insomnia) if not attended professionally and surrounded by a safe community (family, friends, partners, etc). This is unfortunately, not a fiction story...
10/10 for beautiful illustrations and writing portraying all these complex situations, not an easy read if you have been through similar trauma or are not mentally ok with handling mature content like this