A fifth grader who deals with sensitive issues while growing up. She is worried about the people around her and tries hard to help them when they are in need. This leads to her trying to handle issues such as her first menstruation alone. Although Tsubomi is a responsible and helpful girl, she is naive in a sense that she does not understand many things around her. She is happy about her mother's pregnancy. She is troubled about lot of things like the strange feelings that she has around Nemoto, the "indecent things" that her parents have done to make a baby, and her feelings towards Saya when she gets close to Nemoto. Tsubomi is shown to have feelings for Nemoto but does not quite know it herself at first. She later confesses to Nemoto, and the two become a couple.