MXLT -- SMUT

Zhen Lixin is affected by an Aphrodisiac-- a potion that arouses one's sexual desires. And the only cure is to have those desires fulfilled.

Zhen Lixin and Wei Xiyang are staying at an inn in a foreign town. When Lixin was strolling down the town, he accidentally crashes into a stall that sells potions. He manages to save the potion bottles from falling and breaking, but one manages to slip-- an Aphrodisiac. It scatters near him and he gets affected.
His life was of virtue, so he had no experience with such things. Though he was good at controlling his desires before, the Aphrodisiac gives him a hard time. That's right, a 'hard' time.
His only hope is to satisfy his yearnings.

Thankfully, there's a prince of hope-- Wei Xiyang.

NOTE: The image on the book cover is not my art.