The movie starts out with Katsuhiko going to the US, with Kasumi and Yusaku seeing him off at Narita. 
Two years later, Katsuhiko is a professional racer, and comes back to Japan to race (and to marry Kasumi). Yusaku`s hobby is photography.

The story focuses on the relationships of Kasumi Kishimoto, a high school student. When she enters Myoujou High School, she moves into her aunt's boarding house, where four boys attending the high school are tenants. Despite her steadfast determination to stay loyal to her boyfriend, who is studying abroad, Kasumi finds herself slowly falling in love with one of the boarders, Yuusaku. 
 
(Source: Wikipedia)

Kishimoto Kasumi, a 15-year-old girl, was supposed to live at her auntie's house in order to go to high school since April. However, when she moved to the house she was surprised with the fact that there were already four new male students living in the same house. To make the matter worse, that day while she was taking a bath, Takasugi Yusaku, one of those boys, came into the bath and saw her naked. This is how Kasumi's troublesome high school days started. 
(Source: AniDB)

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