H-Era Year 3: The legendary rap group The Dirty Dawg has disbanded, an unprecedented event driven by sudden animosity. Ex-members Ichirou Yamada and Samatoki Aohitsugi receive invitations to participate in the first iteration of the Division Rap Battles—a new initiative by the Party of Words that pits the best of each division in Tokyo against one another for territory, pride, and a substantial monetary prize. Due to their hatred for each other, both men form their own respective teams to compete. Ichirou joins forces with his younger brothers, Jirou and Saburou, to form Buster Bros!!!. Meanwhile, Samatoki strikes a deal with corrupt police officer Jyuto Iruma and ex-Navy member Riou Mason Busujima to form MAD TRIGGER CREW.

Using the power of rap, both groups fight their way through their respective division qualifiers to represent Ikebukuro and Yokohama. As the two teams clash with each other, the dispute that caused the rift between Ichirou and Samatoki begins to unravel into a complicated situation involving Japan’s new matriarchal government.