Sae Kawano inhabits Maison du Wish, a boarding house filled with students ostensibly preparing for university entrance exams. Like her housemates, she makes scant academic progress, embracing a slothful existence. She belongs to a group of young students sharing the cheap apartment, collectively defined by their lackadaisical approach to studies and daily life. This stagnant routine faces disruption when her younger sister unexpectedly moves into the boarding house. The sister acts out of concern, viewing Sae as irresponsible and neglectful of family duties, hoping cohabitation will instill discipline and focus.

The sister's presence introduces tension as she observes and attempts to counter the pervasive idleness of the residents, targeting Sae's habits specifically. Despite this intervention, Sae remains firmly entrenched within the group's relaxed dynamics. These dynamics involve frequent aimless activities and persistent academic disengagement. Her interactions with fellow residents Yurume Aida, Kumi Tanaka, and Matsukichi actively reinforce this unproductive lifestyle, enabling its continuation. Available information documents no significant long-term changes or personal development resulting from her sister's influence.

Her background indicates a move to Tokyo, likely for academic reasons. Beyond the sister's current involvement, no further details about her family origin or prior history are given. The boarding house setting and her relationships within it solely define her current circumstances; no additional backstory is provided across the manga, OVAs, or anime adaptations.