假面骑士们的战斗结束了，黑暗零食也从这个世界消失了，时间悄然流逝。万事屋“欢乐游行”为留在人类世界的砂糖人们介绍工作，“人类与砂糖人的共存”本应正逐步实现。但有一天，绊斗和在街上遇到的受伤少女们一同前往了“狩藤医院”。
那是一家看似可疑的医院，专门为那些不方便去正规医院的人看病，但医生狩藤的医术十分高明，绊斗对接受治疗的少女们的日常生活感到好奇，便偷偷跟踪她们，没想到她们的团体中竟然有那个莉泽，失去了父亲博卡、留在人类世界的莉泽，如今似乎成了不良少女们的保镖。
此外，绊斗注意到团体中有一个年轻男子，于是决定去调查他，结果发现这名男子竟是砂糖人，他似乎正企图再次让黑暗零食流通起来。
绊斗心情复杂，突然胸口一阵剧痛袭来，曾经的改造手术对他的身体造成了严重影响。而且，对博卡心怀怨恨的砂糖人·伊吉克也出现了……

本剧讲述患有相貌失认却拥有惊人记忆力的休职警官狗饲锥（平祐奈 饰），与因暴力问题被调离搜查一课、但检举率第一的刑警猿渡响（丸山隆平 饰）组成搭档，共同挑战长期未解的离奇案件。两人在破解谜团过程中建立信赖，直面彼此的创伤，是一部融合推理与人性描写的悬疑剧。

Rinne Kudo, who is studying abroad in England, sees her classmate kidnapped by Yoko Minato right in front of her. Rinne returns to Japan with Sophia's guidance, who is investigating a series of female kidnappings, and decides to investigate the case with Girls Remix. They head to the scene of the crime with Reika Shindai to investigate a case suspected to involve an alchemist. At that moment, Yoko appears again and attacks them, but a woman who looks like Clotho appears and fights Yoko. Will Rinne be able to solve the case and save her classmates?!

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.

本剧讲述了在“机场占领事件”过去一年后，前刑警武藏三郎（樱井翔 饰）成为警视厅刑事部人质事件对策班（BCCT）搜查员，再次卷入前所未有的危机。东京都知事选举特别节目直播中，电视台突遭戴着妖怪面具、自称“妖”的武装集团占领，500名人质命悬一线，三郎的妻女也身陷其中。面对恐怖分子的威胁，三郎联手BCCT成员及警视厅新搭档，全力展开营救。随着“那个男人”的再度登场，一场暗藏巨大阴谋的极限战斗悬疑剧再度上演！

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?!

蒙面武装组织再度来袭，占据电视台并劫持500名人质！挺身而出的，是那个男人——武藏三郎（樱井翔 饰）。新的敌人究竟是谁？他们的目的又是什么？谜团接连浮现，极限倒数的战斗悬疑剧，正式开幕！最糟的一天，再度来临。

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！