Kyoushashou

[MangaDex]

 

[Duainfey]

Reminds me of that old short story" That Hell-bound Train" by Robert Bloch. Don't really see this as something that can be serialized but as a oneshot I found it fairly decent.

 

[Jayde_The-Grand-Duckmaster]

Interesting!
Rather peculiar and just a tad confusing at first glance, but definitely promising! I actually just went and read some more Kinashi Runamu because of this. Dark and gritty-- definitely. A thoroughly engaging story with dynamic characters and an intriguing premise-- absolutely.
To be honest, it reminds me of another manga I read a while back, Detective Xeno and the Seven Locked Room Murder Mysteries, and also really enjoyed.
Maybe you'd want to check that out if you were entertained by this oneshot (and obviously more of this author's work if you haven't already).