Fuu Hououji, localized as Anais in certain regions, ranks among the three primary protagonists. As an eighth-grade student, she possesses sandy blond hair, green eyes, and round glasses typically absent in full armor. Her attire transitions from a school uniform—green jacket with white collar, green skirt, and red bow—to white-and-gold emerald-studded armor upon arriving in Cephiro, later upgraded to a green feathered armor dress. Previously enrolled in a private school for intellectually gifted children, her summoning occurred during a Tokyo Tower school trip where she met Hikaru and Umi; transported together to Cephiro, she remained calm and facilitated introductions.

Characterized by logical intellect, strategic thinking, and a polite yet blunt demeanor, her strengths include archery from school club training and a firm belief in collective will. Despite occasional self-doubt, she confronts challenges with determination. Her wind-based magic specializes in defensive and supportive spells: "Winds of Healing" (Iyashi no Kaze) for recovery, "Winds of Protection" (Mamori no Kaze) for barriers, and "Winds of Admonishment" (Imashime no Kaze) for immobilization. Offensive capabilities include "Emerald Typhoon" (Midori no Shippu) and the anime-exclusive "Emerald Cyclone" (Midori no Zenpuu). Initially wielding a bow, she later acquires the heavy sword Escudo, liftable only by her. She pilots the bird-like mecha Rune-God Windam, awakened during her journey.

Key developments involve her relationship with Ferio, Princess Emeraude’s brother, met in the Forest of Silence. The manga shows him gifting a ring that sparks her romantic feelings, while the anime features a communication device. Their bond deepens during the second arc as Fuu wrestles with guilt over Emeraude’s death, bolstered by Ferio’s steadfast support. When captured by the Fahren faction during Cephiro’s crisis, she wins freedom via an archery contest against ruler Lady Aska, forging friendship. Ferio later rescues her, reinforcing their connection.

The OVA’s alternate continuity portrays her as less polite and more assertive. She joins a music club, plays piano, and battles Cephiro’s invasion of Earth, piloting Windam against Ferio. Post-mission, she returns to Earth masking internal grief. Reuniting with Hikaru and Umi at Tokyo Tower, she transports back to Cephiro to defend against invading nations, providing strategic battle support and aiding in dismantling the Pillar system that centralized the world’s stability. The manga concludes with periodic visits to Cephiro, sustaining her bond with Ferio, who associates her with his happiness.