Natsumi Bekki, commonly referred to as Becky, is a teacher at Tamo Agriculture School where she serves as the homeroom instructor for class 2-A. Despite her youthful appearance, she is approximately forty years old and has never been in a romantic relationship, a fact that weighs on her and contributes to a sense of loneliness. Her personality is marked by extreme and unpredictable mood swings. At one moment she can be cheerful, playful, and openly mischievous, often tricking her students for her own amusement. In the next moment she may become gloomy and melancholic, expressing deep dissatisfaction with her single status and life circumstances. She is also an avid otaku, deeply immersed in anime and related hobbies.

Her students have given her the nickname Around Forty as a teasing reference to her age, but when she becomes genuinely angry she assumes a feared alter ego known as Gaia. In this state she can suddenly plunge the entire class into despair with her overwhelming presence and sharp demeanor. Her role in the story is primarily that of a supportive yet chaotic teacher. She frequently interacts with the main characters, especially Kosaku Hata and his classmates, offering guidance, stirring up trouble, or providing comic relief with her unpredictable behavior. Her motivations seem rooted in a desire for connection and companionship, though she often masks her vulnerability with theatrical antics. Notable abilities include her skill at creating a tense classroom atmosphere through sheer mood shifts and her capacity to command respect and fear when she unleashes the Gaia persona. Over the course of the series she does not undergo significant personal development, remaining a consistent source of humor and occasional heartfelt moments as a lonely but caring educator.