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

The Dragon Queen and Prince Uno turned up after a few days with a ton of bags full of gifts – mostly for the babies.

"Are you showing signs of dark magic?" the Dragon Queen asked Fang as soon as she saw him. "Is Rhea showing any signs?"

"I don't know," Fang said honestly.

"Rhea had a burst of magic similar to Daddy's when she was born," Ray spoke up. "But after that, she hasn't shown any signs of magic at all."

The Dragon Queen sighed. "I'd hoped it won't come to this," she murmured. "The original royals of the Valley Kingdom did possess dark magic, but it was a well-kept secret. Your mother told me about it because she was worried that either Una or you may inherit it from her side of the family. She had a bit of dark magic herself, but it wasn't very powerful. At most, it could be used for small, everyday things. Una doesn't have any dark magic at all – hers is entirely from our side of the family."

235 – A Sealed Box