BL with pretty purple hair mc

A guy tried his sister's game (I think) and got teleported into the game or sum. In the game he has long, purple hair, and I'm pretty sure he looks just like someone that other characters know (I remember he doesn't know anything about the character he got reincarnated into). He woke up not knowing what's happening but the two guys who live in the house with him helped him learn about the world. It's a harem, I remember this really hot vampire guy and a really hot big guy who are head over heels for him.