Bakemonogatari 03 (Engelstalig) - Manga

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.