小石川 光希 (Koishikawa Miki, 小石川 光希
Miki is a lively high school student, who is on the Toryo High School tennis team. She is cheerful, friendly, supportive, outspoken, tomboyish and good-hearted. On the other hand, she can also be insecure, whiny, clingy, and very emotionally dependent on others. She had a part-time job working in an ice cream parlor, called Bobson's. Later, she works in a small decoration shop.
When she was in junior high, she confessed her love to a male friend of hers named Ginta, but it was a disaster and Miki ended up heartbroken. Eventually she got over it and became friends with him again.
While Miki was in high school, her parents went on a trip to Hawaii and decided to swap spouses with another couple. The other couple had a son the same age as Miki, and they all moved into a large house to live together. That boy was Yuu Matsuura, and Miki started to fall in love with him as they came to know each other better. However, Miki was very uncertain of herself and became jealous because Yuu was always surrounded by other girls, several of them being very beautiful while Miki believes herself to be only average-looking.