"VF" means to battle with the card game "Vanguard", in other words, to "fight". The criminal's demand is to call the strongest adult vanguard fighter, and to fight him against three games.

Then Toshiki Kai, a cool-hearted high schooler, introduces Aichi to a card game called "Vanguard". When participants battle they picture they are on a planet called "Clay", and since Vanguard ...