Kouta Kazuraba works hard as a part-timer and he thinks that he would like to be a different person in the future. One day, he happened to pick up a Sengoku Driver, the tool for transforming into an Armored Rider, in the forest and started fighting as Armored Rider Gaim to save the people from the monsters named Inves, who came from a different world.

日本黑道「集英組」第二代的高中生一條樂，雖然暗戀著女同學小野寺小咲，卻為了阻止黑幫鬥爭，而與另一個黑幫大小姐桐崎千棘假裝成一對戀人，而這齣暴走喜劇在加入了「警視總監」的女兒橘萬里花及殺手鶇誠士郎之後，更是一發不可收拾…