Abandoned at birth near the Asahi Orphanage, Yuki Sakurai carries profound loneliness and a fear of abandonment. He possesses an empathic ability to perceive others' emotions and memories through physical contact, often causing him intense distress. This power manifests as "Kami no Hikari" (God's Light), a pure yellow light capable of purification and healing. As the central figure of the Giou Clan, he is the master of the Zweilt Guardians, warriors dedicated to his protection. Yuki's abilities evolve significantly. His "God's Light" heals injuries by absorbing others' pain and wounds, frequently resulting in severe exhaustion and prolonged unconsciousness. He also develops the defensive "Hallowed Wall," creating protective barriers of yellow light that require intense concentration and drain his life energy. Despite his gentle and self-effacing nature, he demonstrates skill in martial arts. A critical aspect involves reincarnation. Yuki's soul has been reborn multiple times across centuries, with all previous incarnations being female. His current life as a male represents a significant divergence, potentially signaling an end to the cyclical conflict between the Giou Clan and demonic forces or reflecting a desire to escape past traumas. He retains no conscious memories of past lives, experiencing only lingering nostalgia, particularly around the demon Luka Crosszeria. His relationships define much of his development. Luka Crosszeria, a powerful demon from the "sinner" clan Crosszeria, has protected Yuki since birth. They share a profound, centuries-old bond stemming from a past life where they were lovers. This connection transcends gender, with Luka devoted to Yuki's soul. Yuki also forms close bonds with the Zweilt Guardians, especially his distant relatives, the Murasame siblings (Tsukumo and Toko). Initially reluctant to rely on others due to his fear of burdening them, he gradually learns to accept support and embrace his role. Yuki's background reveals he is the son of Mizuki, who abandoned him for his safety. He later moves to the Twilight Mansion under the guardianship of Takashiro Giou, who claims to be his brother, leading him to adopt the name Yuki Giou. His journey involves uncovering the truth about his origins, his purpose within the Giou Clan's war against the Duras demons, and the nature of his connection to Luka. The narrative concludes without fully resolving all aspects of his past, including the complete history with Luka and the implications of his gender transition across incarnations.