Shimaisou

On a winter day, my younger sister's body plummeted into the courtyard of Kagome Seishin Girls Academy.

A sanctuary to young girls, a paradise for lambs.
Like this place, my sister closed herself off from the world long ago, drifting in space until gravity brought her down.

She escaped with her life intact, but fell into a coma.

And now I, Hoomuku Tooku,
and my friend Mizuumi Shizuku,
are looking for the reason that my sister fell --

[Edited from DLSite English]