Rascal-sensei, also known as Kaskal-teacher, serves as the homeroom teacher for the Banana Class at Urara School. He sports long hair, sometimes tied back with a yellow bow, and maintains a strict demeanor, frequently using a whip to enforce student discipline. Despite this stern exterior, he possesses a fundamentally kind heart and demonstrates protective instincts toward his students, taking action to shield them from threats.

His background features a longstanding rivalry with Mayachon-sensei, the Orange Class teacher, originating from academic and personal competitions during their own school days. Mayachon harbors romantic feelings for Rascal-sensei but resents his consistent kindness toward everyone except her, fueling ongoing tension between them.

Key episodes illustrate his character. Episode 2 shows him exhibiting peculiar behavior after a magical mishap affects the school principal. Episode 7 highlights his absence due to an accident, leading to a substitute teacher and emphasizing his importance to the class. He further demonstrates his protective nature by safeguarding his students from external dangers. His documented appearances are limited to the original anime series.