After the Third World War, the world descended into chaos and a matriarchy was established in the power vacuum. In Japan, a new female-only government controls the country, forcing the male population to live outside of Chuuouku. Furthermore, the "H Law" is put into motion, which prohibits all weaponry; instead, people must fight battles using devices called "Hypnosis Microphones" that directly affect the opponent's mind through lyrics.

A year later, a conflict in Ikebukuro rises between two factions: "Mad Comic Dialogue," lead by gang member Samatoki Aohitsugi, and "Starway to Heaven," of which 17-year-old Ichirou Yamada is a part of. Both of them are bound to confront each other in order to gain more territory in the district.

Elsewhere, medical specialist and former assassin Jakurai Jinguji meets the cheerful but mysterious Ramuda Amemura after Ramuda saves him from a rebel attack at the hospital where he works. Impressed by the new musical technology, Jakurai asks Ramuda to teach him how to rap and become a mic-wielder.

When the four men join forces by pure chance, they realize they have what it takes to gain control of all divisions in Japan and fight against the unjust system created by Chuuouku. But everything might not go as well as they planned when their enemies are closer than they expected.