Takaoka, Mika

Mika Takaoka is a 16-year-old high school student who works in a cafe. Confident and mature for her age, she is a lesbian, and surprisingly secure in her sexuality.

[Spoiler] When she was younger, a woman named Sayaka Yoshiwara was hired to tutor her for her high school entrance exams. Mika fell in love with her and eventually tried to kiss Yoshiwara in her sleep. Yoshiwara reciprocates her affection, but not her feelings; later, Mika sees Yoshiwara on the street with a man, and when she confronts her about this, Yoshiwara tells her that she's "just having fun".

This experience provides the backbone for her characterization. Fast-forward to the present and she is more confident about her sexuality, but also colder and more aloof towards other people and the idea of romance, opting to chase after older women and no-strings-attached sex instead of finding love, primarily because she doesn't want to go through the same experience she had with Yoshiwara. [/Spoiler]

[Spoiler] Towards the end of the manga, she runs into Yoshiwara and confronts her peacefully, finally gaining some closure and moving on with her life. [/Spoiler]