March 1956. Tokyo is slowly rebuilding from the war a decade prior. Private detective Reiji Tokisaka takes on three cases almost simultaneously: a girl in Inokashira Park who wants him to find her true self; a wave of murders his childhood friend Sergeant Uozumi needs investigated; and two missing students from Oba Girls' Academy, where Tokisaka's sister attends. Entering the academy undercover as a teacher, he meets the park girl again — Toko Kuchiki, whose voice is light and clear and whose casual manner does not match it. As more victims surface and the numbers stop adding up, a cold case from six years ago begins to look like the key to everything.