
This is fucked up but I wouldn't call it grooming. The older brother was forced into a parenting role which in itself is abuse. The younger brother is obviously traumatised for a couple of reasons and has no one else except for his saviour. They're heavily codepended and this sick intimacy turns into sexual desire. So again, I wouldn't call this grooming, it wasn't intentional on the older brother's part, rather it seems like he's trying to control himself but eventually gives in to temptation (big part of the fauxcest trope). They're both in need of therapy but neither is evil.

I don't like this ML. He's not a red flag or anything but he seems like a douche.

Yeah like kinds self absorbed so he doesn't realize how much his actions or inactions or laid back attitude could affect people around him. It's not intentional but that's the problem, he's not an intentional person and kinda just goes with the flow. Which sucks for gunjoon because you can tell he's very emotional and overthinks
Why is he so gorgeous oh my God