Kumi Tanaka lives at Maison du Wish, a boarding house for young students retaking university entrance exams, known as "rōnin." She shares the space with fellow residents Yurume Aida, Sae Kawano, and Matsukichi.

Within this group, Kumi frequently masterminds predictable schemes, relying on her housemates' participation to create minor conflicts or humorous situations in their daily life. Despite this manipulative streak, she fully embraces the collective lifestyle defined by procrastination and a lack of serious exam preparation.

The arrival of Sae's younger sister introduces a potential disruption to the residents' routine. However, Kumi, like the others, shows no meaningful shift from their entrenched habits of distraction and complacency. Her background, history prior to the boarding house, and individual development throughout official media adaptations remain unexplored.