Well I had a BAD experience with Japan customs. It was mostly my inexperience and naivety that resulted in a few being confiscated. I planned a trip to Cambodia some friends asked that I pick up some Rolex's if they appeared decent. While there I also bought some real gem stones, bracelet, earrings, etc. So on my entry declaration form back into Japan I listed the valid jewelry and upon seeing this the agent asked to see the merchandise. Well they saw the watches too.... after a couple hours of inspections and multiple questions / answer sessions the watches were seized and I had to hand write a letter of apology to the head of customs - but the let me in the country and I went back to work for a few more months. Surprisingly multiple entries down the road with one or 2 rep's I was not stopped ever again, kinda figured I would be put on a "watch" list..
Lessons learned, no more buying for friends, separation in the baggage incase opened, wear the replica, pack the Casio's and smudge / dirty up any rep's to appear well used if found.