I still don’t get why professor cha is obsessed with wooju?

It's because his half-brother is obsessed with Wooju

So does that mean he’s obsessed with His half brother? I initially thought professor cha HATED wooju but there’s a panel of him possibly ing him and now he’s admitted to kidnapping him. I’m so confused. Does he want a three way relationship atp

Yes that's in fact correct, he's obsessed with his half-brother and that logically means that he needs to kidnap Wooju and then later on in the story facilitate his half-brother bitch him. It's genuinely insane in a way that makes me gasp but then start laughing. This is like no soap opera I've ever seen, and I kind of love it for that I can't lie.