Ah, here's a nice table for the hex head sizes. JIS stands for something like Japan Industrial Standards; DIN is Deutsches Institut fur Normung ("German Institute for Standards").
Bolt Depot - Metric Bolt Head, Wrench Size, and Diameter Table
So 7, 8, 10, 12, 14, 17, 19, 22 are the wrench sizes for older Japanese cars. Not sure about current ones, though. They may use the ISO ones.
-soD