Sayuri Hayama is third grade high school student whose mother died two years ago and lives with her father Keigo. One day, Keigo is remarried to Madoka, which became Sayuri's mother-in-law and her daughter, Yui, as her sister-in-law. She does not accept the sudden event when Yui made a kiss to her.

Sayuri thinks straight to Yui. The next day, she became sick, and Yui takes care of her which will change their relationship.

While Sayuri is asleep, Yui kissed her. Sayuri noticed it and in the next morning they result in awkwardness. Sayuri goes to her neighbor's house instead of her home which Yui doesn't know.

Being questioned by Yui, Sayuri noticed her feelings and kissed. Yui speaks to herself that their relationship between Sayuri became closer. Sayuri later confessed confess to Nao and Mirai on how she is feeling now.

Sayuri is stunned that she and Yui directly liked each other. Yui notices Sayuri's thoughts, and gently hugs her. When they later sleep in bed, Madoka saw them.

Yui and Sayuri's parents, Madoka and Keigo wanted to know their relationship. Keigo questions to Sayuri, who remained silent, and Yui tells that she is serious. The next day, Yui disappears.

Yui and Madoka leaves the Hayama's house. Later Sayuri saw Madoka, and gives information about Yui. The sisters' relationship is missing.