It all started when an American tourist asked a police officer for directions to the Kinokuniya bookstore in Shinjuku Ward, Tokyo.

The Californian, 74, could never have imagined the officer would reply to his question with: "Do you have a knife?"

He could never have dreamed, either, that his possession of a pocketknife, which he calls a "customary personal item," would be illegal in Japan and lead to 10 nights in detention, the man told The Japan Times during a recent interview.