Legend said, whenever you saw grim reaper, that means your time will be over soon. You saw these grim reaper since you're a kid. And then he keep following you, like your own bodyguard.

He's a grim reaper. He's kind, a little bit cold, sometimes harsh, but good, kind and friendly. He's pretending to be your friends in school, and pretend to be normal human even though he's a grim reaper.