Obtained: Speak with Yajirobe at Sacred Land of Korin in the West Forest Area during the main story War at the Door
Objective: Catch 2 Goliath Catfish and 1 Scarlet Catfish
Travel to the Sacred Land of Korin in the West Forest Area and for the northwestern part of the map near the lake to find Yajirobe on a dock. Speak with him and agree to his fishing challenge. Head to the fishing spot at the end of the dock and fish until you catch the requested fish. Then speak with Yajirobe to complete the story.