Premise posted:

Year XXX.
The world lost one-third of its population in World War III. Those in power who feared the destruction of humankind are not armed forces. They tried to avoid war by discussion. But the foolish men couldn't end their conflicts. And the last year of the known era, the existing world ended by the hands of women.

H Era.
The armed war was eradicated. Under them, all conflict, small or military-scale was replaced by the use of a special device mesmerizing the psyches of the people. Its name is Hypnosis Microphone. The lyrics channelled through this microphone can affect human sympathetic nerves, parasympathetic nerves, etc. It became possible to alter one's state of mind.

H Era, 3 years ago.
The superiority or inferiority of a man is determined by rap. Outside of the Chuohku District, men live in the Ikebukuro, Yokohama, Shibuya and Shinjuku Divisions. Groups of MCs representing their division would fight over territories with the power of music, with the loser of a rap battle having to hand over a part of their territory to the winner.

In this world, where words, not weapons, became tools of power, the battles for territories holding men's pride and prestige begins.