"Hypnosis Mic -Division Rap Battle-" is set in a dystopian future where Japan is divided into several territories, each controlled by a different faction. The central conflict revolves around the use of "Hypnosis Microphones," weapons that convert spoken words into destructive energy. These microphones have replaced traditional weapons, and battles are now fought through rap battles, where the power of words and rhythm determines the outcome.

The story primarily follows four rap groups, each representing a different division of Japan: Ikebukuro's Mad Trigger Crew, Yokohama's Buster Bros!!!, Shibuya's Fling Posse, and Osaka's Dotsuitare Hompo. Each group consists of three members, each with distinct personalities and rap styles. The narrative explores their rivalries, alliances, and personal struggles as they compete in rap battles to gain control over territories and resources.

Mad Trigger Crew, led by the stoic and disciplined Samatoki Aohitsugi, includes the hot-headed Jyuto Iruma and the enigmatic Rio Mason Busujima. Buster Bros!!!, led by the ambitious and protective Yamada Ichiro, features his younger brothers Yamada Jiro and Yamada Saburo, who bring youthful energy and raw talent to the group. Fling Posse, led by the charismatic and flamboyant Ramuda Amemura, includes the serious and strategic Gentaro Yumeno and the energetic and unpredictable Dice Arisugawa. Dotsuitare Hompo, led by the laid-back and enigmatic Sasara Nurude, includes the cheerful and optimistic Rosho Tsutsujimori and the mysterious and reserved Rei Amayado.

The plot unfolds as these groups navigate the political and social tensions of their world, engaging in intense rap battles that serve as both a means of conflict resolution and a form of artistic expression. The series delves into the backstories of the characters, revealing their motivations, fears, and aspirations. Themes of loyalty, identity, and the power of words are central to the narrative, as the characters grapple with their roles in a society where words can literally shape reality.

As the story progresses, the groups face various challenges, including internal conflicts, external threats, and the looming presence of a powerful organization known as the Chuuoku, which seeks to control the Hypnosis Microphones and maintain its dominance over the divided nation. The series builds towards a climactic confrontation, where the fate of the territories and the future of Japan hang in the balance, determined by the outcome of the ultimate rap battle.