Ummm.. do you realize he raped her?? The title is DARVO card on FL. She didn't steal shit. He did. Her virginity. Her first night. And her everything after that. Plus, he's obsessively jealous. Gets jealous of her only female friend, of the said friends fiance who's also his childhood friend, and of small kids even who are at the receiving end of her kindness and/or attention. He wants to be the only person in her life that she gives attention to. I don't know how this manhwa is a romance actually and why people are dying on the "Zeronis is a green flag" hill. Just lack of discernment or enablers in real life, idk. Anyway good job spotting his narcissistic toxic traits.
I read this a long time ago, while i was a bit younger. Now that I'm rereading it(start of the manhwa) I think Duke is just...insufferable. unbelievable. Take a hint bro when someone is saying they don't want you. I got so angry at him. Flowing with overconfidence, they think the world is there to bend for them, even people. What arrogance.