Height 165 cm A third year high school student who is close to failing every class except math. He is a laid-back person whose only real friend at school is Tsubasa Hanekawa. Due to events prior to Kizumonogatari and Bakemonogatari, Koyomi avoided having friends and seemed to have lost faith and trust in people and himself.

Spoiler

During spring break, he gave Kiss-Shot his blood and became a vampire. Although Meme Oshino helped him become human again, there are a few lingering side effects; he can see in the dark and far distances, and he heals faster than the average human. He is still scared of morning sunlight even though it no longer has any effect on him.