It’s an otherwise normal October night in the Akihabara district in Tokyo as tourists and locals alike plod along the glowing neon streets. Young women in maid outfits beckon half-heartedly to men ambling in and out of ramen shops, PC parts suppliers and anime retailers.

Several floors above? It’s fight after fight to the death.

Figuratively speaking, of course — combatants grasp not steel katanas but carbon fiber batons laden with accelerometers and other sensors, all wrapped in foam to soften the inevitable blows. They swing not to maim or kill but for points, though there’s still a palpable, primal aggression in the air when two competitors face off.