Few genres are as freighted with the politics of authenticity as hip-hop. Just last month, the New Yorker kicked off a fresh round of controversy when it ran a profile of Lord Jamar, a cantankerous middle-aged rapper who rails against what he sees as the softening — and whitening — of modern hip-hop. In between lambasting Le1f's sexuality and Kanye West's stylistic and sartorial liberties, Jamar took aim at artists like the white rapper Macklemore: "You are guests in the house of hip-hop. . . . Keep it real with yourselves: you know this is a black man's thing."

What, you have to wonder, would the man dubbed "hip-hop's alpha conservative" make of a group like Simi Lab? Even the more enlightened Western listener can tend to regard Japanese hip-hop with mild condescension: Fun, maybe even sincere, but no substitute for the real thing (whatever that is). Yet there's enough about this eight-strong, mixed-race crew to give you pause.

Try watching Simi Lab's latest video — for its riotous, superhero battle-rap anthem "Avengers" — and you'll probably find yourself asking the same questions many Japanese fans did when the group's first promo went viral in 2009: Who are these people? And what language are they actually rapping in?