Fudatsuki Kenji is infamous at school for his delinquent behavior and his unwavering devotion to his sister, Kyoko. Despite his reputation for a sister complex, Kenji's true affections lie elsewhere, directed towards Hibino, the only girl unfazed by his tough exterior. The twist in this tale? Kyoko is not an ordinary sibling but a jiangshi, a powerful vampire who relies on Kenji's blood daily to sustain herself. Bound by a ribbon that governs her behavior, Kyoko transforms from a temperamental being to a sweet and apologetic sister once it's removed, albeit with a dangerous inclination to attack. As Kenji navigates the challenges of protecting others from his sister's nature and grappling with his feelings for Hibino, the question looms: can he prevent his sister's harm and potentially win over his crush amidst the chaos?