The Branch of Reincarnation is a mystical item that bestows the abilities of a person's previous lifetimes, but the price is the user's own life, as they must cut their own throat with it. Touya Senji, a high school student burdened by self-doubt, feels overshadowed by his exceptionally gifted sibling. Convinced that academic achievement is his only path to recognition, he pours himself into his studies, yet remains unsatisfied despite placing among the top one hundred in national practice exams. His life shifts dramatically when he witnesses Haito Luo Buffett, a classmate and a Returner who has unlocked her past-life abilities through the Branch, fighting against a serial killer.
