Don't buy the liquid duty free on the plane to NRT. You do have to go through security, and they will take anything that doesn't fit the 3-1-1 rule. Wait until you clear security at NRT, then buy your duty free there. Lots of duty free stores with all that stuff down a single long corridor. Or, you can buy inflight duty free from NRT to SEA, but you're taking a chance they may not have exactly what you want.