Koudai Oozora is the father of Tsubasa Oozora and husband of Natsuko Ozora.

Koudai works as a Sea captain and is away most of the time, so the boys are raised mostly by their mother. Daichi was born sometime after Tsubasa left Japan. He is very good friend of Roberto Hongo and even prevented a suicide attempt of him. Captain Oozora even went so far as to recommend Roberto to go to see a famous Ophthalmologist in Japan in the city of Nankatsu. There, Roberto in return of Koudai's help and letting him stay as a guest in the Oozora residence, he became a mentor and teacher of Tsubasa in order for the latter to develop and polish his natural football talents and learn the basics to become a future pro football player.

(Source: Captain Tsubasa Wiki)