Kazuma Mutsumi is the older brother of Asuma Mutsumi who is a student teacher that teaches at the same school where Asuma is attending. Kazuma's hair color, eye color, and height are the same as Asuma Mutsumi, but Kazuma's hair is much more ragged and he has a mole under his left eye. Kazuma is normally seen wearing suits while teaching at school. When he isn't working or out, Kazuma wears casual clothes. Kazuma's personality is similar to Asuma Mutsumi to some degree. While he shares his brother's open-mindedness and generosity, Kazuma is a bit more childish. He wore a battle helmet during his card battle match with Asuma. He left a treasure for the new History members after his graduation. He seems to be unaware of the fact that he was unpopular with his peers during his high school years. Like Asuma, Kazuma shares a love of history and is kind to anyone. An example is when Kazuma offered to buy his class ice-cream as his way of showing gratitude for their cheering during the match. Due to his friendly and upbeat personality, he was well-liked by both female and male students. However, Kazuma is more mature when it comes towards women. Kazuma became extremely popular with the female students. Asuma was aware of his brother's reputation as a womanizer. Kazuma would flirt with any woman who developed an attraction for him or any woman he himself felt attracted to. An example is when Kazuma tells the class that he will give a kiss to anyone who got the wrong answer, much to the joy of his female students and the chagrin of the male students, especially Kae Serinuma's suitors. When Kazuma met Kae, he became interested in her despite the fact he is a student-teacher and the one supervising her class during his teacher-training. Kazuma abandoned common sense when he declared to Kae's suitors that he would go after her, much to their surprise. Like Shima Nishina, Kazuma has a keen sense of perspective as he was able to defeat Kae's suitors one by one during their attempt to stop him from chasing after Kae. Although Kazuma shares a close sibling relationship with Asuma, he was the one responsible for Asuma's fear of the dark. He did several pranks on Asuma, knowing that Asuma would be too slow to notice the pranks. Kazuma is very determined to get whatever he want and declared that he always get his hands on what he want. Regardless, he congratulated Asuma for defeating him during their card battle. Kazuma gave his support for Asuma to go after Kae, whom he noticed that Asuma fell in love with.