Uki Uki Tsuri Tengoku - Ningyo densetsu no nazo begins when the player's character (a fisherman) is taken by a plane to Mermaid Island (a fictional place where there are a lot of different fishing spots). The game features conversations with the island people and different fishing spots (with different fishing types) and lures.

Easy to use and with a great variety of fish species the game got a great database of fishes and features a lot of hours of play. All the game use a first person perspective in the adventure and the fighing part. The player can fish on land or use a boat to go to other fishing spot of the island.