There's actually a pretty famous, super old story in my-slash-our world - like, medieval old - but I dunno how popular it is in Japan.

Uh, Dante's Inferno. It basically codified the idea of there being nine circles of Hell in the western-Catholic idea of the place.

I don't... really know if that helps, but recurring numbers cannot be a coincidence right now. [not with Fortune heading this round]