Masataka Sawatari, commonly known by the nickname Waseda, is a mathematics teacher at Sainotama Girls' High School. He first supervises Class 1-2 and later becomes the homeroom teacher of Class 2-2. He is a strikingly handsome man, twenty-seven years old and unmarried, with a birthday of October 21. His nickname is derived from his alma mater, Waseda University, a prestigious institution he graduated from. In terms of personality, Sawatari usually fulfills the role of the straight man in the chaotic classroom environment, offering dry reactions to the eccentric behavior of his students. However, he is not without his own quirks: he openly admits to a preference for college-aged women, a trait that the girls in his class find both amusing and embarrassing. He also possesses a hidden talent as the Vocaloid producer known as Teishotoku-P, a fact that remains unknown to most of the students. Akane Kikuchi, nicknamed Wota, is an avid fan of Teishotoku-P's music and, unbeknownst to herself, is gradually developing romantic feelings for her teacher, though she remains in denial about it. Sawatari's role in the story is primarily as a supporting character who provides comedic tension and occasional guidance. He often serves as the target of the students' antics, but his genuine care for his class occasionally surfaces. His development is subtle, mostly revolving around his secret identity and the growing, unspoken connection with Akane. Notable abilities include his mathematical competence, his proficiency in music production, and his ability to maintain a calm demeanor in the face of absurdity. Despite his own shortcomings, he remains a stabilizing presence in the girls' otherwise wasteful high school days.