On a rainy day, the elite salaryman Amakusa Ryo almost falls down some stairs when he is saved by an ordinary high school girl named Arima Ichika. Ryo was dizzy from not eating breakfast, which worries Ichika and she offers him her lunch then runs off. Later when Ryo gets home, Ichika is in his living room and he finds out that she is actually his sister Rio's classmate. Ryo wants to thank Ichika for saving his life and offers to kiss her...

Ichika and her friends talk about romance in class as the time for Christmas and their school trip draws near. Ichika is asked what kind of guy she likes and tries to describe someone exactly the opposite of Ryo. However, Satsuki then points out someone who actually fits that description. Meanwhile, one of Ryo's coworkers hears him talking to Ichika over the phone and hears that he addresses her as "Ichika-san" as well as him telling her that he loves her...

A few days after they went flower viewing, Ichika is anxious because she hasn't heard from Ryo since and she decides to talk to Rio about it. Rio tells Ichika that she should try contacting him herself, which Ichika is rather nervous about. Rio tells her that she feels sorry for her brother because Ichika won't make up her mind on how she feels about Ryo. Ichika builds up the courage and finally calls Ryo, but he tells her that he's busy with work and won't be able to talk to her for a while as if he's trying to keep his distance from her...