The high school girl whom the nameless salary-man begins a relationship with after the two crash into one another on the stairs of a train station. Feeling guilty for breaking his arm, she visits him several times in the hospital allowing the two to get to know each other better.

During the day she attends high school and serves as the class representative. She also works part-time as a waitress at one of the Koubeya chain of bakery-restaurants where she wears the signature bowtie and tartan-pattern apron uniforms. She has a younger sister in middle-school who is also well endowed.

She prefers to be referred to as "Ai-chan" named after her cup size.