A mysterious door suddenly appears in front of Shoma and Sachika. Shoma is dragged through a door and arrives at a peaceful world where Dark Snacks don't exist!? There is also a Hapipare in that world, where a young man with a gavv named Taorin works. However, he has no memory of any of his past. Shoma helps Taorin to recover his memories. Meanwhile, a man calling himself "Caries" begins to attack the town indiscriminately, turning the peaceful world upside down! As the two struggle to restore peace, they arrive at a giant house of sweets where they were about to grab something, but Caries transforms himself with an unknown Gochizo and hunts down Shoma and his friends! What is the source of the overwhelming power that the strongest enemy has acquired? Kamen Rider Gavv's great adventure beyond time and space begins now!