Gengorō Ōnabara

was an instructor at the Shinigami's Shin'ō Academy.

History
Ōnabara was the Head Teacher of Class 1 of the first year students. In this capacity, he was the teacher of Momo Hinamori, Renji Abarai and Izuru Kira when the three of them first joined the Shin'ō Academy. On their first day, he gave a welcome speech to the students of Class 1, praising them for their success and telling the academy's expectations of them.

He was also the teacher of Makoto Kibune, who went to him to seek answers for why the Gotei 13 refused to recruit Kibune, despite Kibune being a top student. Ōnabara replied that while it is true that Kibune was a top student, grades were only part of the equation and that Kibune must learn what he lacks on his own.