The Shinigami began as a Japanese importation of the western Grim Reaper and took off in various odd directions in Japanese pop culture since then. Sometimes Shinigami are fearsome monsters, sometimes they’re basically superheroes. There’s an urban legend that the Shirogane Tunnel in Tokyo is a gateway for Shinigami. Some have seen screaming faces in its pillars and spectral figures that can be seen only for a moment.