Bad Trip summary: As a lowly yakuza, Kousuke sells his body to men for a living. And although he usually leaves the place quickly after sex, he accidentally finds himself waking up in bed with a customer the next morning. What's more, for some reason, he can't remember last night at all. Despite seeing Kousuke's tattoo, Inami, an incredibly handsome customer, asks him to spend one more night with him. Inami's strange friendliness just confuses Kousuke at first, but he becomes suspicious of him after hearing a rumor about "Pierce", a drug recently gaining popularity on the market that can make one's memory blurry. In fact, Inami is a detective who is also looking for the source of Pierce......