Kaede Tatsunokuchi is a high school girl and one of the main supporting characters in the film. She is a close friend of the protagonist, Nagisa Yukiai, and a natural rival to another classmate, Yuu Hamasuka. Kaede is portrayed as being athletic, competitive, and headstrong. To support herself or gain experience, she works part-time as a waitress at a local family restaurant.

Her primary distinguishing trait is her intense, long-standing rivalry with Yuu. This competitive drive originates from a past sense of envy, leaving Kaede determined to finally compete against and prevail over her rival. However, she finds that she consistently fails to win against Yuu, who bests her at every turn. This dynamic is established at the film's start, where Yuu is made captain of a rival lacrosse team and soundly defeats Kaede's team. These feelings of ill-will are a major component of her early characterization.

Within the group of friends that forms to help Shion Yazawa, Kaede serves as a spirited and determined member. Despite her initial animosity toward Yuu, her role in the story involves gradually overcoming her personal grudges as the girls unite for a common purpose, leading to her development from a purely competitive individual into a more collaborative team player. Her notable abilities include her physical prowess and athleticism, particularly in the sport of lacrosse.