I'm on chapter 18 and I'm sorry but this is practically rape. He said the word "no" many times, he tried to stop Geumwoo many times. Earlier, when they were together in a dream, he also said "no" many times. And what pisses me off Geumwoo told him that he was too tense. It's not him who's too tense, it's you who's too aggressive, dude. It's your fault, stop blaming others for your behavior, you just can't control yourself and you don't care if you hurt someone. "No" means "no".
His behavior is toxic and forcing sexual intercourse is terrible.
I bet that the stepmother is a killer and is obsessively in love with Adler, she probably killed his mother and father...
or Archduke killian is killer, who knows ╮( ̄▽ ̄)╭