Mizuho Kobayakawa is a young Japanese woman characterized by brown hair, blue eyes, a height of 1.64 meters, a weight of 48 kilograms, and physical measurements of 83-56-82. She was formerly a member of the Sakura Junior High School tennis club. At approximately twenty years old, she attends a New Year's Eve class reunion where she reunites with fellow club members. During this reunion, she looks forward to seeing Tatsuya Kubo, for whom she harbored secret feelings during their school days.

Following the reunion, the group organizes a ski trip to stay at a lodge within a hot spring resort owned by Mizuho's mother. However, Mizuho's mother falls ill, creating a conflict for Mizuho between her desire to care for her mother and her pursuit of a romantic connection with Tatsuya.

Mizuho Kobayakawa appears as a main character in multiple official installments of the "Class Reunion" series. She features prominently in the 1997 original OVA "Class Reunion: Yesterday Once More" and its 2002 sequel OVA "Class Reunion Again," where the first episode specifically focuses on her story segment. She also originates from or appears in a related visual novel game.