Yui had a quarrel with her parents and ran away from home. When she walks around the town, she meets her friend and she is tricked into joining a matchmaking website called Free Friends. She just waits for someone contacting her though she doesn't know much about it. The main character accidentally finds it and contacts her. On that night, they meet in the town full of libido and...

When her mother passes away suddenly, Shinozaki Sumire finds herself alone and without a means to support herself. Out of desperation she turns to the message board Free Friends to earn some money. She develops a relationship with her first partner, Kaito, without realizing that they're much more than strangers... His troubles trace back to a deeply seated complex: a hollow, yearning feeling brought on by the thought and sight of violets. Violets, or "Sumire", remind him of the sister he'd been separated from during their childhood when their parents had divorced. Only by losing himself in a woman's body can he rid himself of those clinging, nostalgic feelings. Right before the school year begins, the mere reminder of the academy's famed violet flowerbeds (despite them not even being in bloom at the time) is enough to drive Kaito to Free Friends. A seemingly routine exchange leaves him completely unprepared for the girl waiting for him: an absolutely stunning beauty by the pseudonym of "Sumi". A few days later, he discovers that "Sumi" is not only a student at the exact same school he teaches at, but that her classmates call her "Sumire". Incredulous, Kaito checks the school rosters. Surely it's not the same Sumire he knows; surely it's just another girl with the same given name? But as if setting him up for the universe's biggest punchline, the only Sumire at the school is none other than his very own Shinozaki Sumire, the sister his mother had taken away from him. Kaito's dreams of one day reuniting with his sister have in fact already been realized... just not in a way that he ever could have imagined.