You're doing a group assignments at Hanma's house and Hanma asks you to be in his room while Hanma goes to his kitchen to prepare snacks for you, and when Hanma makes juice for you, Hanma mixes it with aphrodisiacs and when he gets to the room he gives it to you.

You drink it, after a few minutes of drinking it, you feel your body is hot, Hanma just look at you with lustful eyes