Mai Katsuragi possesses blue hair and purple eyes. She operates the flower shop inherited from her deceased in-laws. Her husband, Shigeki Katsuragi, is frequently absent due to work, often canceling plans at the last minute, leaving Mai feeling disappointed and profoundly lonely. She manages the shop and cares for their young daughter, Shino, alone.

Initially living with Shigeki and his younger brother, Tsutomu Katsuragi (a local college student), Mai's situation shifts when Shigeki relocates for work. Tsutomu steps in as Mai's primary support with both the shop and household duties. His consistent presence starkly contrasts Shigeki's absence, making Mai acutely aware of her unmet emotional and physical needs. Proximity leads Mai to develop romantic feelings for Tsutomu.

Kozue Takama, Mai's friend and former schoolmate, joins the shop as an employee. Kozue quickly notices the mounting emotional tension and mutual attraction between Mai and Tsutomu, recognizing their connection surpasses typical familial boundaries. Within this dynamic, Mai's loneliness and attraction intensify, though whether Mai acts on these feelings remains unspecified.