Masataka Sawatari, nicknamed "Waseda" after his Waseda University alma mater, guides Class 1-2 at Sainotama Girls' High School as their homeroom teacher. This nickname firmly identifies him among the students.

His duties include running remedial sessions starting the very first day for academically challenged pupils like Nozomu "Baka" Tanaka. He frequently delivers corrective lectures addressing the academic and behavioral shortcomings of Tanaka and Minami "Yamai" Yamamoto, ranging from private talks to public actions like physically restraining them during assemblies.

Beyond teaching, Waseda secretly operates as the Vocaloid producer Teishotoku-P. This alias remains hidden even from his student Akane "Wota" Kikuchi, an avid fan of his music. He participates in Vocaloid producer fan conventions under this identity.

Personally, Waseda harbors a specific romantic attraction to female university students, a preference he openly acknowledges during class introductions but conceals to protect his career, framing it as incompatible with teaching. His student interactions extend beyond academics; he consults Yamai about her chunibyo delusions, often resulting in comically broken glasses when her statements escalate. He also employs food bribes to encourage student dialogue.

In the live-action adaptation, an original mini-drama titled "Robokko," set a century before the main story and centering on Shiori "Robo" Saginomiya, features Waseda without altering his core character.