Kira, sole heir of the Okibi dynasty—the capital's wealthiest family—resides in their sprawling, isolating estate. Her father, factory magnate Yuoshichi Okibi, and mother, the calculating Hibana, oversee a household where Kira's childhood is marked by profound loneliness. This isolation fuels her deep craving for companionship, leading her to embrace newcomers Koushi and his sister Hinako as instant siblings and friends. Kira radiates bright energy, curiosity, and empathy. She bonds fiercely with Hinako, treating her as a cherished younger sister and vigilantly tending to her well-being. Though prone to daydreaming and infectious optimism, Kira occasionally reveals thoughtlessness—like celebrating amid others' grief—highlighting a flighty streak that starkly opposes Hibana’s cold pragmatism. Their friction peaks over Kira’s assumption she’ll inherit the family factory, a claim Hibana openly disputes. When Koushi arrives at the estate, Kira is immediately fascinated, guiding him through the grounds and eagerly pursuing friendship. Her vibrant presence, symbolized by sunlight-like yellow dresses, leaves an indelible mark on Koushi. Yet their connection unfolds against Yuoshichi’s treacherous backdrop: covert skyfire energy research and conspiracies targeting the divine clans ruling the capital. Later, Yuoshichi—driven by Flickering Flame motives—attempts to murder Kira. Koushi, Hibari, and Hibana intervene, sparking a violent clash where Yuoshichi and Hibana gravely wound each other. Kira survives only to undergo a cataclysmic metamorphosis, becoming the living vessel of the Flickering Flame. This transformation binds her to the world’s primordial mysteries and humanity’s fraught ties to higher powers, placing her at the epicenter of debates on the Earth’s annihilation and civilization’s fate.