In a war-torn orphanage where death is a common occurrence, Sheena Totsuki is deeply affected by the ongoing conflict unlike her fellow orphans. After encountering a bloodied yet cheerful girl named Mimi Kagari on the night of her roommate's death, Sheena is surprised to find Mimi joining her class as a new student the next day. Rumored to be immortal, Mimi becomes Sheena's new roommate, hoping to blend into school life. Despite their budding friendship, Sheena wrestles with Mimi's indifferent stance towards the war, challenging her perception of their harsh reality.