Originally Posted by
andymo99
Yes, you do.
Absolutely. You will go through the US formalities during preclearance at YVR, though, so at least you won't have to deal with it at the connecting point traveling westbound.
The reverse itinerary (NRT-USA-YVR), though, would involve going through US customs/immigration at the first point in the USA, then going through Canadian customs/immigration at YVR.