Musubi is a sentient rice ball and one of the five main students at Ryuuguu Elementary School. He is especially talkative and displays a quick temper, notably becoming angry whenever someone mistakenly calls him onigiri instead of the more proper musubi. His background is rooted in the traditional Japanese folktale Omusubi Kororin, which is his favorite masterpiece and a source of inspiration for his own desire to become a noteworthy character. Underneath his irritable exterior, Musubi has a tsundere side, showing a strong, if sometimes awkward, interest in the protagonist Meisaku Matsuda. He is a loyal friend to his classmates Sweets, Nokio, and Bolt, and he often participates in the group’s chaotic adventures at school. Over the course of the series, his relationships deepen, especially with Meisaku, and he learns to be more open about his feelings. Musubi has several brothers—Tsuna, Takana, Katsuo, and Taro—who are also rice ball characters. While he does not possess overt supernatural abilities, his rice ball form is central to his identity, and his quick wit and constant chatter make him a memorable and often humorous presence in the story.