Note that in Japanese, the number 3 reads 'mi' and 7 reads 'na', so 373 = Minami.

Izumi is nervous before a championship game, so Koji makes him feel better with graphic fluidy sex in the shower. Izumi goes on to the game (with Wakashimazu and Hyuga as team mates) and kicks soccer butt.

(Source: zetsuai.org)