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...

Ichika and Rio go to Okinawa for a school trip. Masuda ends up coming along with one of his seniors at work to be their camera guy on their trip. Rio had been sending pictures to Ryo from their trip, which ends up reminding Ryo of Kai and he gets worried. Meanwhile, Ryo ends up picking up an anime keychain that his coworker Matsushima Arie had dropped and she asks him to not let anyone at work know about her hobbies, and he has something nice to say in return...

Ryo's coworker Arie has been working as long as he has and is a secret anime nerd. They get a little closer after they talk about some anime. Arie starts to realize that she has feelings for Ryo and invites him out to dinner with some other coworkers. Meanwhile, Ryo drives Rio to Ichika's house after he finds out she's spending the night there. Ryo gives Ichika's mother various presents, making her ask him to come inside, but...

On the morning of Valentine's Day, Ryo is waiting by the front door like some pet waiting for their owner to come home. Ichika finally comes by and tells him that she spent days trying to figure out what to get him for Valentine's Day other than chocolate and she gives him something rather surprising. After getting to school, Ichika meets up with her friends and they exchange chocolates. Kai receives a message from Ichika asking if they can meet during lunch. Meanwhile, Arie also had prepared some chocolates and...

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...