It says under my “Activities” tab that I have defeated 5/6 of the masters.
When I go to Poyaqui I cannot initiate the last game though? Is it some sort of bug or am I missing something obvious?
EDIT: For future reference to anyone who gets this bug, I have found out that I needed to bring the character that beat Irongut in order to fight Poyaqui. Bringing any other characters (even if they beat the earlier opponents) will not allow you to fight him.