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

When Ren woke up, he found Fang's anxious face poring over him, and Dr. Gordon and Steward Paul hovering in the background.

Not this again, Ren thought wryly.

"What happened?" he asked, and to his dismay, he found that his voice was rather hoarse.

"You fainted, you delicate flower," Dr. Gordon replied in his usual acerbic style. "You will give Fang a head full of grey hair before he becomes old enough to get married to you with your current physique! Now that you are learning medicine yourself, and I'm told that you are something of a genius in the medical field yourself – shouldn't you at least take the basic care of your own body? How will you treat other people when you are so fragile yourself?"

112 – Dr. Gordon Reappears