After Earth Eleven returns to Earth following their victory in the Grand Celesta Galaxy, they are greeted by a mysterious letter. This "paper" is an official challenge delivered to the team.
The letter reveals the existence of Shadow of Orion (or a variation of "True Inazuma Japan" depending on the translation), a team made up of players who were originally candidates for the national team but were "discarded" or replaced by the Earth Eleven members. Inazuma Eleven Go Galaxy Episode 33
This episode serves as the buildup to the final confrontation on Earth, where the legitimacy of the Earth Eleven is challenged by those who feel they were unfairly left behind. Context within the Series After Earth Eleven returns to Earth following their