Apparently an old friend of Saji and Yuki. Both him and Saji joined the team at the same time to pick up girls. He once asked Koizumi out and she shot him down saying that it would just be a waste of time. It is because of that, that he often gets furious with Saji and tells him to stop acting like Koizumi's boyfriend. He shows up near the end of the anime trying to make Saji come to practice and ends up challenging him to 3 on 3 basketball with Koizumi being the prize. Even though Hitachi and his team won against Saji, Koizumi still rejected Hitachi and left him heartbroken again.

(Source: Wikipedia)