Miki is a vibrant high school student who plays on the Toryo High School tennis team. She is known for her cheerful, friendly, supportive, outspoken, and tomboyish nature, as well as her kind heart. However, she can also be insecure, whiny, clingy, and emotionally dependent on others. Miki works part-time at an ice cream store called Bobson's and later transitions to working in a small decoration shop.
During her junior high school years, Miki confessed her love to a male friend named Ginta, but it ended disastrously, leaving her heartbroken. Despite their friendship, Miki was shocked by this outcome. Eventually, she moved past it and rekindled their friendship.
In high school, Miki's parents went on a trip to Hawaii and decided to swap spouses with another couple. This other couple had a son the same age as Miki, and they all moved into a large house together. That boy was Yuu Matsuura, and as Miki got to know him better, she began to fall in love with him. However, Miki felt uncertain about herself and became jealous because Yuu was often surrounded by other girls, many of whom were very attractive, while Miki considered herself only average-looking.
