突然、翔馬とサチカの前に謎の扉が現れる。ショーマはドアから引きずり込まれ、ダークスナックが存在しない平和な世界に到着します！？その世界にはハピパレもあり、タオリンという名前のギャブを持つ若者が働いています。しかし、彼には過去の記憶がありません。ショーマはタオリンの記憶を取り戻すのを手伝います。一方、「キャリーズ」と名乗る男が無差別に町を攻撃し始め、平和な世界をひっくり返す！二人が平和を取り戻そうと奮闘する中、何かを掴もうとした巨大なお菓子の家に到着するが、キャリーズは正体不明のコチゾと変身し、ショーマたちを追い詰める！最強の敵が獲得した圧倒的な力の源は何でしょうか？仮面ライダーガヴの時空を超えた大冒険が今始まる！
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!
