Bakemonogatari manga volume 1 features story by Nisioisin and art by Oh! Great.

One day, high-school student Koyomi Araragi catches a girl named Hitagi Senjougahara when she trips. But—much to his surprise—she doesn’t weigh anything. At all. She says an encounter with a so-called “crab” took away all her weight…

Monsters have been here since the beginning. Always. Everywhere.