Student of Private Academy Clanmine, Shirogane Mitsuki, repetitively experiences a dream wherein an elder brother he doesn't have dies protecting him.

An Absolute Hierarchy System that is determined by the uniform, an elder brother who shouldn't exist, and an un-enterable clock tower that nobody has ever set foot in...

When the hidden truth behind this warped school is brought to light, a fateful adventure awaits!

The story of the nine stage girls from Seisho Music Academy and their daily lives before the TV Anime!