Kensaku Ono

Kensaku Ono (大野 健作) is the homeroom teacher of Class 3-D in Kunugigaoka Junior High School and the former teacher of Nagisa Shiota and Karma Akabane.

Appearance
Ono has short dark brown hair with thin-shaped eyes, and mostly seen with a serious expression and lightly tanned skin.

Personality
Like many of the faculty of the main building, Ono is antagonistic and cruel, occasionally towards Class E. Ono is also very uncaring as he doesn't care about the well being of his students or how they behave unless it benefit his reputation as a successful teacher.

However, despite his support of Gakuhō Asano's education policy, he expresses shock when the chairman plans to supercharged the final exams to be solved with college-level subjects.

Karma Akabane
Karma is a former student of Ono's. At first, Ono acted friendly and supported Karma due to his good grades. However, after Karma beat up a classmate for bullying an E Class student, Ono's true nature was revealed as he betrayed him. Enraged, Karma wrecked his office, and birthed a newfound hatred for teachers until he was rescued from falling to his death by Korosensei a short time after joining Class E.

Nagisa Shiota
Ono showed very little patience towards Nagisa and even called him an "unteachable brat". According to him, he got the worst teacher's review of his career because of Nagisa. He seemed happy upon Nagisa's transfer to Class 3-E but the two haven't been seen interacting since.

Quotes
(to Karma Akabane) "Are you out of your mind or just stupid?!"

(to Gakuho Asano) "Wait, all this just for the math portion of the exam?"