Jaywalker_Holmes

Ren, a modern doctor and a secret master magician, suddenly finds himself inside a random book he picked up at the airport...as the villainous older brother of the protagonist. As the bad guy, he's supposed to make life difficult for the Male Lead until the latter grows up and kills him in revenge. However, looking at the broken teenager in front of him, Ren can't help but feel his heart soften. 
Fang was an orphan who had never known what a family is. Abandoned at birth, all he knew was pain and fear. He loved nothing, and wanted nothing...until he saw the angelic Wade. To save Wade, Fang didn't hesitate to sacrifice himself. ..after all, there was no one to cry over him.
But then, Ren appeared and turned his world upside down.

The Villain Saves the Male Lead

Princess Una froze when she caught sight of Ren, and at the expression on her face, Fang, too, turned around and saw Ren in the doorway, looking impossibly pale.

"Chairman Ren, it's not that Fang doesn't care about you – he does, very much so. It's just that he is very young, and he has confused gratitude and affection with romantic love. Please forgive his inexperience and allow him to have a clean break up with you," Princess Una said gently, ignoring the twinge in her heart that occurred at the sight of Ren's pale face.

The man really looked as if he was about to disappear into thin air, she thought with a sigh. She would have actually liked to have this man as her brother in law, in fact, but at the moment, Fang's welfare was more important than anything else in her mind.

167 – Explanations and Realisations