In Giant Killing a ragtag bunch from East Tokyo are struggling in Japan's top football league. The team is going through an abysmal spell right now where they are nearing the bottom of the table and have lost five matches in a row. Losing hasn't done much to team morale, because it was already at a low. Fan support, on the other hand, is also looking bleak.
In the world of football, once the fans turn on a team, the end is near. The team doesn't recover, coaches are fired, players are sold, and the team drops to lower divisions. In a situation where profits often prevent them from ever being successful again against even the mediocre top division programs... ETU, East Tokyo United, has only their coach to blame.
ETU hires a new coach that once played in ETU. This coach wishes to prove to his ex-players and fans that even against the biggest clubs in the nation, he can make the team win.
(from Nihonmaru, edited by Ge4ce and Kouri-chan because of unclear sentences.)