The protagonist, Kajiki Mitsuru, is wandering about in this world, tormented by nothingness, chaos and despair.
---"Why am I still in this world of despair...?"
The only person he trusts from the bottom of the heart is his little sister Semi Haruna.

One day, he finds a scrap of paper in his shoe rack on which the name "Tousawa Yoshimi" is written.
Who has, for what sake, put that in there...?
"Tousawa Yoshimi" --- this is the name of a character who appears in Mitsuru's dreams.

The next day Mitsuru hears of a girl, Futami Moe, who is searching for Yoshimi.
Why does she know of him...?

Diorama is a story about perception, love and insanity, in which the real world and a parallel world intersect.

[From DLSite]