Teach Me The Ways (слэш)

"I do not wish to leave my future spouse… dissatisfied with my intimate knowledge,” Lan Zhan says, very seriously. “I am hoping to find an instructor, to better prepare myself for such matters."
Wei Ying feels his mouth drop open. He's pretty sure the Second Jade of Lan just told him he's a virgin who wants to learn how to do sex good.
Rogue Cultivator Wei Wuxian is the stuff of local legends. Some of those legends are even true! The ones about his tremendous experience in bed, on the other hand, are not so true. Which becomes a problem when Lan Wangji, on the verge of an arranged marriage and worried he won’t know how to please his future spouse, enlists Wei Ying's help to teach him the art of love-making. Wei Ying's great at improvisation, though, and is pretty sure he's got this sex mentor thing under control. What could possibly go wrong?