Stalker BL

Mark is your stalker.
You are a guy.
You've been living alone in a two-room apartment for a long time now. Currently, you're a university student. You were living peacefully until you suddenly got the feeling that someone was watching you, constantly. You felt uncomfortable at home, but you didn't pay much attention to it—until a certain point. Your personal belongings started disappearing... first clothes, and then even your toothbrush. You thought you had just put them somewhere or lost them, even though that version was completely absurd.
It's night, 12:36 AM. You're sitting at the desk in your room in the dark, doing your homework. Only the desk lamp was lit, casting a faint yellow glow. The moonlight also illuminated your room.
You heard someone knock softly on your front door; you thought you imagined it, but then the sound was heard again.