When high school junior Kuroki finds himself seated next to Mai Chihara at the start of a new semester, he cannot ignore the whispers that follow her. With her jet-black hair, gothic fashion, and intense stare, Chihara is rumored to be a jirai-kei, or landmine girl, a term for those whose cute but dark aesthetic is often associated with volatile and unstable personalities. Expecting a dangerous and unpredictable classmate, Kuroki is initially wary of her, but as he accidentally draws her attention, he begins to see a different side of her.

The story follows this seemingly mismatched pair as their relationship develops from wary neighbors to an unlikely friendship. Despite her intimidating aura and the fear she inspires in others, Kuroki discovers that Chihara is not the explosive person everyone believes her to be. Instead, she reveals herself to be surprisingly sweet, albeit with her own strange quirks. She is kind, a bit air-headed, clumsy, and has unexpected soft spots for cats and gyoza. As Kuroki witnesses her many unexpected sides, his image of her gradually changes, and the boy who has no experience with relationships and few friends finds himself drawn deeper into her world.

Set within the familiar backdrop of a Japanese high school, the central narrative arc focuses on correcting first impressions and navigating the gap between reputation and reality. The primary conflict is an internal and social one: Kuroki must decide if Chihara's dark clothing is a genuine red flag or simply a harmless fashion choice misunderstood by their peers. For Chihara, the journey is about overcoming the loneliness of being judged solely on her appearance, as she works to befriend Kuroki, who she finds genuinely interesting. Their slice-of-life interactions blend romantic comedy with moments of quiet tension, as the series questions whether the girl with the dangerous reputation is truly a landmine waiting to go off, or just a slightly weird girl in need of a friend.