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

Pax and Wolf returned to Cosmopolis after sorting out the new office in Sand Country. For the next few months, at least, they could easily supervise it remotely, which effectively gave Ren and Fang enough time to get over Fang's exams. By then, the medical institute would be fully ready as well, and the young couple could be happily on their way to becoming certified doctors!

However, the world seemed opposed to letting the couple live in peace for too long. Five weeks after their return, an unexpected VIP turned up unannounced in Ren's office and despite his extreme reluctance to meet him, Ren had no choice. He couldn't afford to cause an international incident by being openly hostile to a foreign monarch, after all.

The middle-aged king of Dune Country was a well-maintained and handsome fellow - of course, he couldn't hold a candle to Fang. However, his eyes were shifty and his entire demeanour rather unpleasant.

90 - A Truly Shameless King