Successfully complete the indicated task to unlock the corresponding fishing spot in the fishing mini-game:

Master Den: Fish up Saboten Crest in the Secret Reaches.
Middle Reaches: Get five "Perfect Fishing" in the Lower Reaches.
Secret Reaches: Fish up Saboten Bond in the Upper Reaches with Matamune.
Taikou Chest (treasure): Get nine "Perfect Fishing" in the Master Den.
Upper Reaches: Get five "Perfect Fishing" in the Middle Reaches.