there was this BL where it was like this demon king of like purebred vampire came to the human world to find a queen or whatever and he finds this guy who lives with his mom and is still in high school. but the first time they met, the supernatural dude scared the other dude, and then he was like your the one, and then he moved in next door to the human dude and then the mom went on a trip and the supernatural man started harassing the guy and they ended up kinda sorta living together, i forgot what it was called :( sorry i felt like that was a lot of words.
Have you read this?
http://www.mangago.zone/read-manga/sweet_blood_kim_se_young/
you never realize how much you love someone until you lose them.