An hijacking incident as occurred! Genta and Yukimi, alongside several other passengers have been kidnapped by the criminal named Azuma and taken to the forbidden land known as Area 666. The Igarashi siblings rush to save the hostages, but are met with Azuma, who transforms into Kamen Rider Daimon with a strange belt in his hand. He attacks the Igarashi siblings with the intent of judging humanity himself. The mysterious scientist Soutomi, who was kidnapped alongside Genta and Yukimi, then reveals a great secret within the Igarashi family and hunts them down, while setting up a trap that prepares them for their greatest crisis ever. At the end of the fierce battle with Azuma, what will become of the ultimate buddy that Ikki and Vice have? Will it shatter or transcend into an unwavering bond?