At midnight, transfer student Mio Tsukishiro suddenly wakes up in an empty school. Dark red lights, silent corridors, a staggering figure heading toward the classroom... The familiar campus has become an anomalous space beyond the reach of reason: the Zero Realm.
Hunted by strange entities, Mio Tsukishiro receives help from exorcist Kuri Gu and shrine maiden Byakuya Jinguu. She soon learns that once the Zero Realm has chosen you, you may be pulled back into it when the midnight bell rings.
To regain her peaceful daily life, Mio has no choice but to use her eyes, which can see what ordinary people cannot, and investigate anomalous events lurking in the shadows of the human world alongside her companions.
Forgotten rumors, sealed rooms, missing people, and inexplicable deaths will all be recorded one by one in their casebook...
