Glass hails from a world of Spirit People facing annihilation by recurring Waves of Calamity. Chosen as the wielder of the Vassal Fan, she became the Fan Hero. Her world had previously merged with three others through similar interdimensional events, fueling her commitment to survival at any cost. Initially stern, cold, and fiercely loyal to her world, Glass led a mission to kill Raphtalia's world's Four Legendary Heroes, believing their deaths would halt the Waves and save her home. Her combat skill enabled her to easily defeat Ren, Motoyasu, and Itsuki during the Third Wave. However, witnessing Naofumi's resilience against the Soul Eater led her to acknowledge him as the only "true hero." Their initial duel ended inconclusively when the Wave's time limit forced her retreat. Glass endured discrimination within her martial arts school due to her birth circumstances. Though initially barred from the Vassal Fan trial, the weapon chose her after rejecting all other candidates. She later formed a close bond with Kizuna Kazayama, the Hunting Hero summoned to her world. Together they defeated the Demon Dragon Emperor. When Kizuna became trapped in the Infinite Labyrinth and other summoned heroes failed, Glass's world neared collapse. Ancient texts prompted her to target heroes from other worlds as a solution. A pivotal shift occurred when rogue Vassal Book wielder Kyo Ethnina manipulated the Spirit Tortoise in Naofumi's world. Recognizing their mutual goal of preserving their worlds, Glass allied with Naofumi to stop Kyo. This temporary truce solidified after Naofumi rescued Kizuna from the labyrinth. Subsequently, Glass and Kizuna joined Naofumi's efforts permanently to combat the Waves' orchestrators. As a Spirit Person, Glass's power stems from "energy," a fusion of vitality, magic, and soul. High energy enhances her attack and defense, but depletion severely weakens her. Soul-healing water from Raphtalia's world uniquely restores this energy, creating reliance during battles there. In her own world, this limitation demanded strategic adjustments. Later developments revealed diluted lineage to a clan equivalent to Pacifiers, enabling her to synergize with Shildina, the Ofuda Hero, accessing powers that regulate Holy Weapon wielders. Glass's personality evolved from detached resolve to displaying warmth, especially around Kizuna. Naofumi noted her uncharacteristically joyful expressions in Kizuna's presence, contrasting her typically serious demeanor. She held deep affection for Kizuna, symbolized by gifting her a haori. Her relationship with Naofumi transitioned from adversarial respect to trusted cooperation confronting multiversal threats.