I'm probably the worst person to rate this game as I usually avoid fishing in game, but it's one of the good ones. The main mechanic is quite fair and not boring, plus the demon fishes sprites are really cute.
Now outside of the fishing, the movement of the character feels off. I'd like to be able to move diagonally, and the character doesn't seem to stop when I stop pressing. Now that's easy fixes though and quite nitpicky.
That would fit well within a larger game, so good job!