Hiiragi Yatsuse, a high school student known for his kindness and selflessness, finds it difficult to build connections with his classmates. One night on his way home, he encounters Tsumugi, a peculiar girl searching for her mother. Without any clear explanation, Tsumugi decides to stay at Hiiragi's house. With her assistance, Hiiragi manages to escape a supernatural presence that appears in his room. Tsumugi then reveals herself to be an oni. After Hiiragi sees her cherished amulet, he agrees to accompany her to the shrine where she originally obtained it. Together, they set out on a journey to find Tsumugi's mother, encountering new characters and overcoming numerous obstacles along the way.
