Neptunemon is a God Man Digimon whose name and design are derived from the mythological Neptune, the Roman god of the sea. One of the "Olympos XII", it is a Digimon god of the sea which governs all Aquatic Digimon. The Scalemail which covers Neptunemon's body is made of Chrome Digizoid that has been transformed into "Blue Digizoid", which excels in agility, so it is capable of moving at terrifying speeds at sea. It constructed a castle to reside within, the "Abyss Sanctuary", at the far depths of the sea, so that only those who can withstand the water pressure of the extreme depths may enter.