Help me find that BL

I'm trying to find a bl (I think it was a shounen ai) that was a semi-guide verse. The uke (guide) had black hair and red eyes, and wore a white long jacket. He was nice on the surface but manipulative underneath. Although I can't remember much a out the seme I think he worked for the police or something similar, and he had a kid sister that really liked the uke. Sorry if all of this is vague af XD