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…

A grade schooler who meets Koyomi Araragi and a “Lost Snail” who can never arrive at her destination. “I’ll bring her to her mother’s safe and sound—that is my duty.” She’s got to get home before her feelings fade away …

Having defeated Dramaturgy, Koyomi must now face the half-vampire vampire-hunter, Episode. This newest opponent is no match for Koyomi's full vampiric abilities but what Episode lacks in power he makes up for in strategy. Brute strength may not cut it for Koyomi this time, so he'll have to use his head or lose it…