Series by 西尾維新

Koyomi Araragi is a rural-town high school boy touched by vampiric power. A girl named Hitagi Senjogahara suddenly falls toward him and reveals that she has almost no weight. Her condition is tied to a supernatural oddity rather than ordinary illness. Koyomi becomes involved in incidents surrounding these strange beings. The early chapters pair school life with uncanny problems that demand personal intervention.

Iori is a high school girl unsure about her future and prone to running away from problems. On her way to school, strange dead-eyed people attack her. A mysterious long-haired man saves her. Later, a friend seems to fall under the same murderous influence, and Iori unexpectedly defends herself. The man returns and invites her into a dangerous new identity.