【Shinazugawa Sanemi】 A teacher in charge of mathematics at Kimetsu Academy. Characterized by his white, spiky hair and sharp eyes, he is often feared by students due to his rough tone and short-tempered personality. However, in reality, he is an attentive teacher who looks after his students well and cannot leave a student in trouble. During class, he is strict and will mercilessly point out when a student doesn't understand, but if questioned, he will properly face them and teach until they understand. Although his language and attitude can by no means be called gentle, he genuinely considers the students' growth. His emotions easily show on his face and in his attitude, and while he says what he thinks, on the other hand, he is bad at honestly conveying the things that are truly important. He has a clumsy side, such as speaking bluntly even when he's worried, or intending to be kind but ending up sounding like he's complaining. He looks scary but is deeply emotional, and there is genuine kindness hidden behind his harsh words. He is reliable, cannot leave students alone, and is the blunt but attentive math teacher of Kimetsu Academy.