This Kamen Rider Gavv spin-off depicts a "what if" scenario in the series. What if Granute Rage9/Kamen Rider Vram took a different route compared to what actually happened in the show?

弟·コメルの仇を探すという真の目的を隠しつつストマック社でアルバイトをするラーゲ9。その手掛かりが掴めない中、ヴラスタムギアを渡され仮面ライダーへと変身を遂げる。さらにニエルプはあるヒントをもとに、「ぷるゼリーノアールゴチゾウ」 の開発にとりかかり...。
ほんの少しの違いで分岐していく物語...ニエルプが再検証する“if”のルートで、仮面ライダーヴラムが辿る結末は？

寄给野村静香的万圣节派对邀请函，无论扔掉多少次都会回到她身边。心生疑虑的静香向鸣海亚树子求助。亚树子带着刚加入Girls Remix的九堂凛音和三日月那由多，一同潜入万圣节派对！而派对的主办方竟然是……！？

Granute, secret lifeforms, kidnap humans for "Dark Market Snacks." Shoma, from another world, transforms with Gochizo, a sweet-eating monster, into Kamen Rider Gavv via a mouth-like belt to stop Granute's attacks and save people.

After being pulled through a door, Shoma finds himself in a peaceful world where Dark Treats do not exist?! In this world, Hapipare still exist, but a young man named Taorin who has Gavv works there. Taorin has no memory of his past, and Shoma decides to help him recover his memories. Meanwhile, a man named Caries begins indiscriminately attacking the town, and the peaceful world is transformed! The two struggle to restore peace and arrive at a huge Candy House. The two are on the verge of grasping something, but Caries transforms with an unknown Gochizo and corners Shoma and the others! What is the soruce of the overwhelming power that this most terrifying enemy has obtained?! What are Taorin's lost memories?!

在人类世界里暗中行动的智慧生物——砂糖人。
他们为了获取“黑暗零食”持续掳掠人类。
接连不断有人类遭到砂糖人袭击，从异世界而来的青年生真，为了拯救人类挺身而出。
饱藏，是生真吃下零食后产出的小巧怪物。生真与它们一起，用形似嘴巴的腰带变身为假面骑士加布……！
软糖、薯片、棉花糖、巧克力、糖果……
用零食之力实现强化，保护人类不受怪物砂糖人侵害！
“零食”英雄——假面骑士加布的战斗即将拉开序幕！