The peace after Talpa feels earned, so Shikaisen's arrival hits different, he's not another world-ending god, just a sorcerer who knows exactly what the armors are worth, and he wants them. The OVA trusts you remember who these four are and lets them be themselves in downtime before pulling the rug out. It's a story about the cost of being the only ones who can fight, told in two episodes with the clarity of something that knows its own ending.
Peace has finally settled over the world following Talpa's downfall, and the four armored warriors are ready to enjoy normal lives. Ryou celebrates another year, Kento's lottery winnings promise a fresh start, and Sage pursues his studies abroad. Their tranquility shatters when news reports surface of a brutal killer stalking New York's streets, clad in armor that shouldn't exist outside their legends. The warriors cross the ocean to investigate and discover something far worse than a copycat killer. An ancient sorcerer named Shikaisen has awakened to the true potential of their mystical armor and will stop at nothing to claim it for himself. His hunger for power threatens not just the four protectors, but everyone caught in the crossfire of his obsession. Facing an enemy who understands their armor's secrets as well as they do, the warriors must reunite their strength and confront a threat that challenges everything they thought they'd overcome. This gaiden follows them as they're pulled back into conflict when they thought their battles had ended.