Chieri is a recent college graduate along with her best friend Mamiko. They have been teaching at Kouta's school since his second year. Chieri is rather clumsy and she has trouble holding on to her students' attention. She doesn't have much experience with socializing and she depends on Mamiko's guide through life.
Chieri's younger brother passed away 7 years ago. Kouta looks very much like him and she sees her brother in him.
A year ago during Kouta's second year, he helped Chieri with her duties. He left a strong impression on her since it was her first day teaching. It was recently that Kouta started becoming attracted to her.
Chieri caught Kouta looking through a naughty magazine. She requested to see him after class. She mentioned that Kouta's grades were slipping and ordered him to concentrate more in class. Chieri then brought the magazine back to her home and confided in Mamiko about it. She suggested that Chieri consult Kouta's parents about his grades. Mamiko also recognized that Kouta liked Chieri.
Chieri visited Kouta's home 2 days later. She reports to his mother that his grades were slipping. Chieri met with an accident with Kouta. The next day, she confronted him about it. Mamiko noticed that she was acting strangely. The next day, Chieri reasoned that Kouta could concentrate in class after he had a release and volunteered to help him every morning.
If Kouta goes shopping with Kiyoka, Mamiko warned Chieri to not be too emotionally invested in Kouta. The next day, Chieri caught a cold and was absent from school. Kouta visited her home. She revealed that he looked like her younger brother but that she loved him as a person.
A few days later, Chieri recovered and returned to school. After her morning service for Kouta, they bumped into Kiyoka and Shigeaki and they became suspicious of them. Mamiko revealed that she saw them and advised her to be more careful.
The next day, Chieri wanted to end their affair for fear of being discovered.
If Kouta declares his love for Chieri, she accepts his feelings. The next day, he invites her for a date during the holidays. Later, she noticed Kiyoka dragging Kouta for a date and she became sad.
If Kouta forces himself on her, she pushes him away. Mamiko then volunteers to remedy their relationship.
Some time later, Kouta went on a date with Chieri in town. Kouta met Kiyoka during their date but she didn't see Chieri. Several days later, Kouta skipped a class to spend time with Chieri. Kiyoka later revealed that she witnessed their affair and demand that he end his relationship with her.
If Kouta does as she says, Chieri will declare her love for him and try to understand his sudden decision. If Kouta refuses to explain, he follows through with his relationship with Kiyoka and Chieri was left depressed. If Kouta tries to console Chieri, Kiyoka walks in on them. Chieri realized that it was her doing and confronted her. They fought over Kouta and eventually became friends.
If Kouta decides to tell Chieri, he reveals Kiyoka's demand to Chieri.
If Kouta decides to stay with Chieri, he confronts Kiyoka. She argues that he would lead a difficult life if he goes through with his decision. Several months later, Chieri had a baby girl and she married Kouta after he graduated. If Kouta's relationship with Kiyoka is high, he can choose to go with her instead. Chieri reasoned that her relationship with Kouta wasn't meant to be and moved on.
If Kouta decides to request for Mamiko's help, she confronts Kiyoka. Mamiko agrees with Kiyoka that a teacher-student relationship would be very difficult and confronted Kouta about it. If Kouta insists that he loves Chieri, they get married. If Kouta says that he simply wants satisfaction, Mamiko drags Kiyoka into his relationship with Chieri. If Kouta couldn't decide, Kiyoka becomes frustrated with him. Mamiko then gets involved with his relationship with Chieri.