Koyomi, the main character of the story, is a third year high school student who is close to failing every class except math. Shortly before the first novel begins, he was attacked by a vampire during spring break and became a vampire himself. Although Meme Oshino helped him become human again, there are several lingering side effects: he can see in the dark, his eyes turn red when he gets angry, and he heals incredibly fast. As a result he questions his lifespan. These side effects are later revealed to be due to the bond that Shinobu and himself share. He remains scared of morning sunlight despite the fact that it no longer has any negative effects on him. He started dating Hitagi at the end of Mayoi Snail.
Although he is shown to be attracted to the other girls, he turns their advances down due to his loyalty to Hitagi, whom he is shown to be in love with in the novel and anime. Other characters, particularly Mayoi and Hitagi, seem to speculate that Koyomi is a lolicon. Koyomi is the only person who thinks that his family relationship is bad, while Karen and Tsukihi believe otherwise.
