Occupation College student / Ob-gyn Momo Kashiwabara is a supporting character. She is a member of the Literature Club and a friend of Rui Tachibana. She fits the 'Genki' female archetype in the manga as she is constantly an energetic girl with a bubbly personality who is also incredibly eccentric and overly friendly to some people as shown when she gave Rui Tachibana a nickname and one of the dolls from her bag upon their first meeting. As noted by the girls in her class, Momo is also very flirtatious towards boys, flirtations that are rumored have evolved into sexual relations on more than one occasion. She also exhibits a childish side, as shown by her nicknames like "Rui-Rui" and calling sex "making love-love". She has a massive crush on Natsuo Fujii, which has often gone to obsessive extremes like clinging to his arm and feeding him boxed lunches she made without his knowledge. However, beneath her flirtatious and bubbly nature lies deep vulnerability and a possible self-loathing. Her parents have a very bad relationship and they are almost always working, which leaves Momo by herself for nearly whole days on end.

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As a result of this and her poor relationships with her peers, she once began self-harming. One of the reasons she loves Natsuo is due to the fact that despite knowing about her self-harming and her attitudes towards boys, he is still nice to her.

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She has several overlapping scars on her wrist from her "short phase" of self-harm. Very few people, save for her sexual partners and Natsuo have seen them, with the latter being the only one who empathized with her.

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She later falls in love and marries Ritsu Osaka, and has an unnamed daughter by the end of the series.