Ota is the main teacher of the school and later the second-in-command of Exelion, the spaceship used as headquarters for missions in space. Ota completely trusts Noriko and her skills that will allow her to pilot the Gunbuster, an extremely powerful robot able to effectively contrast the aliens. Moreover, Ota was one of the crewmen of Noriko's father's ship; during the unlucky battle in which he died, admiral Takaya refused the last chance of escaping and let Ota go instead. Probably due to this, Koichiro holds Noriko in great esteem and trusts her.