Futaba Anzai is a supporting character in Koi Kaze. She is a high school student and a close friend and classmate of the protagonist, Nanoka Kohinata. Her role in the narrative is primarily as a confidante to Nanoka, providing a sounding board for her friend's thoughts and feelings.

Futaba is portrayed as a loyal and understanding friend. While she is not aware of the true nature and depth of Nanoka's feelings for her older brother, Koshiro, her presence and questions serve to encourage Nanoka to reflect on her own emotions. In this way, she unconsciously instigates Nanoka to better define and understand her own complicated romantic situation. She is a typical schoolgirl whose perspective helps to contrast the extraordinary circumstances of the main plot with the ordinary world of teenage life. Her primary relationship is with Nanoka, and she has no direct connection to the series' darker thematic explorations.