I  

, 僕

The main character in the books is a high school student who studies mathematics after school. He's in his second year at a Japanese high school, which corresponds to 11th grade in the US system. Despite not having a name mentioned throughout the series, he has a quiet personality and wears glasses. In middle school, he spent most of his time working on math problems alone in the library. However, as he progressed into high school, he developed friendships with Miruka and Tetra, and began to work on math problems with them. Although he is conscious of their potential as love interests, he is too shy to initiate a relationship with either one. He acts as both a teacher and student, working on problems given to him by Miruka or Mr. Muraki, while also teaching Tetra. While he may not enjoy speaking before large groups of people, he has no problem speaking up when teaching Tetra and Miruka.