A strange, silent warrior appears. When the Inferno armor is summoned to battle him, the mysterious warrior calls forth his own armor - a black copy of the Inferno armor! Now, the warriors will find themselves half a world away fighting once more to save humanity, but this time, from their own armor!

Ushio is a freediver with strange powers. He and his friends are at a tropical land in search of a rare fish, the Blue Butterfly. This pursuit leads them to Ayuuru, a local girl who might know where to find the legendary fish.