There's this guy I know in his late 50s who, like many Japanese, looks much younger than his age. Blessed with a boyish smile, a flat tummy and jet-black hair — in all likelihood dyed — the man has already retired from employment at an electronics firm and now stands at the door of his second youth.

But it is hard to imagine this fellow playing gateball or cranking out enka at some karaoke blast for the elderly. One would guess his pleasures rest in other directions, like perhaps hanging from his fingertips or maybe disappearing into smoke.

You see, he's a ninja. No, not the mutant turtle type, nor the wisecracking Internet type, nor even the assassin-in-black Hollywood type.