It centers on a family of three teenagers in high school all living together who are unsure which two of them are related to each other due to a reference from an old photograph.

The series was later adapted into a light novel in 2004, which spanned a total of two volumes and, soon after, into a short one-tankōbon manga version (authored by Akikan), which was serialized in MediaWorks's Dengeki Daioh magazine in September 2005.

In addition, the two girls develop feelings for Maiku, forming a love triangle that cannot be resolved until the truth of their relationship is known.

All three main characters are in the predicament of wanting to discover their past versus the risk of losing a romantic relationship.

anime series, scripted by Yōsuke Kuroda, directed by Yasunori Ide, and produced by Bandai Visual, premiered in Japan on the WOWOW satellite television network between July 15, 2003 and October 14, 2003, consisting of a total of 12 episodes.

The series was later adapted into a short one-volume manga version, authored by Akikan, which was serialized in MediaWorks's Dengeki Daioh magazine in September 2005.

The manga introduces another character in the last two chapters, Hanna Miasa, who provides the explanation for the photograph, and Maiku's, Miina's and Karen's background and relation ties.

The characters in the CD Drama are Maiku, from class 1-A: Yamada-sensei, Karen, Miina, Haruko, Akina Sagawa, Futaba Mashita and Harumi Shinohara.