Kumi Tanaka lives at Maison de Wish, a boarding house for students balancing university entrance exam preparations with daily life. She shares this communal space with fellow residents like Yurume Aida and Sae Kawano. Once celebrated as a child prodigy in her early academic years, Tanaka now faces repeated failures to pass the University of Tokyo entrance exams, resulting in her status as a rōnin—a student dedicating extra years to university admission attempts.

Her personality brims with mischief, often manifesting as playful teasing directed at housemates. She particularly delights in unsettling Yurume Aida by sharing frightening stories to provoke fear, extending this habit to lighthearted jokes with others. Beneath this troublemaking exterior lies a fundamentally kind and affectionate nature. Tanaka frequently wears a gentle smile and finds delight in simple daily pleasures, revealing warm-heartedness alongside her prankster tendencies.

Music captivates Tanaka as a significant passion. She actively practices guitar and composes original songs, enthusiastically sharing these creations with housemates and sometimes persuading them to listen. Those around her generally perceive her musical abilities as unexceptional in skill or talent.

Within Maison de Wish, Tanaka maintains consistent relationships through regular interactions with core residents like Yurume Aida, Sae Kawano, and Matsukichi. These exchanges weave together her playful teasing and supportive presence within the group dynamic.