After Transmigrating into a Novel with My Boyfriend, He Turned Out to Be a Native Villain - Chapter 4: What a Buff Stacking

Bai Aoxue, the best mercenary in the 21st century, is accidentally sent back to the Chengxi Dynasty in Great Continent due to an explosion in her mission, and trapped in the first daughter of Prime Minister. After her rebirth, she is set up by her father to marry the 5th prince Jun Yeyan who wears a mask all day long.
In the face of bloodthirsty enemies, discord between brothers, collusion among courtiers and invasion of enemy state, can Bai and Jun resolve the crises? What will happen to their political marriage? How will the fierce battle for the throne end?
With many twists and turns, the book brings you to experience palace revolution, love and hatred thousands of years ago.

- Description from Novelupdates

I became the childhood friend of the protagonist in a novel. The childhood friend who died from taking drugs.

She is the Crown Prince’s fiancee, but on the night of their wedding, an edict was made and she was given off to marry the crippled and paralyzed God of War.

I had to take him home and raise him. There was no bathtub or a large basin at home, so I had to put him in the washing machine for the time being.

It was an hour later before I remembered it again, by which he had been washed extremely clean.

- Description from Novelupdates