"Neptune World" (ネプチューンワールド Nepuchūn Wārudo) is a fanmade world for the Future Card Buddyfight card game. Their motif is based all around the sea, due to the world being a massive influx of sea. Due to this ecosystem, many aquatic life have evolved so that they do not need to go to land since nothing was out there.
Neptune World is based on Control and Field Manipulation. Controlling the game state through various effects by making your opponent play towards your game. All decks in Neptune World affect your opponent's board state and cards through various ways and changes the game state over time in your favor.