http://www.mangago.zone/read-manga/my_little_vampire/
Doesn’t have pink hair but other than that fits your description.
Sorry not this one but thanks for recommending I will read it later
I'm Yours, Blood and Soul
Folklore no gochisou ? if it's not that one, it may be " I'm yours, Blood and soul"
this is what i'm looking for tysm!
there was one manga I wanted to read but I forgot the name. it's about two men with one black hair and one with pink hair I don't remember, but I know a bit about it. the black-haired boy was a little kid and he had to drink blood like a vampire to grow up and had to drink from the pink-haired guy. that's all I remember so if you know please help and sorry for my bad english