You'd never know if you StreetPassed a real ninja, of course

SEGA's Shinobi isn't just the story of a ninja that kills people: Juro Musashi is mortal too, particularly in the new StreetPass Challenge modes revealed today.

The details we have so far reveal that StreetPassing other plays unlocks Challenge maps, which are much tougher than the standard game as you'll die after just one hit. If you can unlock all the maps, you get to play as the legendary Joe Musashi from the original series; finish them all, and you unlock Retro mode, which puts you back in the golden days of "one hit, one kill".

No StreetPasses near you? No worries: you can use Play Coins instead to unlock the maps and earn yourself Joe Musashi.

Here's the trailer and official details to explain more.

The first time going into Street Pass unlocks a random Challenge Map.

These maps challenge all the skills that you have learned while playing the game, but you now die after one hit.

Each time you connect to another 3DS with Shinobi Street Pass data, you unlock one of their unlocked maps on your 3DS and vice-versa.

Unlock all the maps and you can play as Joe in the Replay levels section (the actual game levels).

Finish all the Street Pass maps and you can unlock Retro Mode for the main game, which enables one-hit kills for everyone (except bosses).