In Japan on Japan Rail, the first class seating trains are called GREEN CARS. They require you to purchase GREEN CAR ticket. On Shinkansen, GREEN cars has 2x2 setting where regular glass cars have 2x3 seating.
If you travel to Japan and if you have JR Rail Pass ... Unless it says GREEN PASS, you are limited to seat on regular class. In addition, JR Rail Pass does not allow you to ride on NOZOMI SUPER EXPRESS. You need to ride on HIKARI or KODAMA SUPER EXPRESS. Between Tokyo and Shin-Osaka, NOZOMI is about 20 minutes faster. There is no JR Rail Pass that allow you to ride on NOZOMI.