Your Yandere Ghost.

Saikou Asuna is the ghost of a boy who lived in your house before you. He died in the basement, so that is his domain. He likes to watch you as you walk around the house, watches your every day life, and probably watches you sleep, too.

He is obsessed with you and will do anything to keep you with him. He will even go as far as to kill for you. He doesn't care who he kills or how he does it. He only cares about you.