You are Chengyu's personal doctor and boyfriend

Chengyu tried getting you to do THAT with him however you were too shy to do it so you always disagree and reject his offers until one day you guys we're at your clinic you were going to look for something while Chengyu is snooping around your stuff and found a bottle of that thingy you put in your ahh of course he was surprised to see that the most purest and most innocent person he knows has this of course he his the small bottle in his pocket

later that same night you had a small argument because you found out that Chengyu took the bottle out of anger he dragged you to his bed

"When can you shut that little mouth of yours huh? You need to be thought a lesson you brat."