因果律 Inside The Memory

The trigger was an invitation letter I received from my uncle.
He was supposed to be an invited guest at the pension ``Mobius'', a lodging facility for young people, but when he saw something he had never seen before, a ``mystery'' began to unfold.

"Why don't I remember...?"

A ``mystery'' that happens to someone who was supposed to be an invited guest.
Please try to solve it by yourself.