High school freshman Nao Misumi has known Sena Ikuta, his older sister Rio’s best friend, since he was in elementary school. As a self-proclaimed “sister’s boy”, Nao has always found Sena’s over-familiarity incredibly annoying. Yet, despite being loud, airheaded, and having zero sense of personal space, he could never truly bring himself to hate her. She has always looked out for him just as much as she has for…