The Wasp is 30 feet longer, it is about 10 feet taller, but it's beam is actually 3-4 feet less, although it's flight deck is a good 15-20 feet wider.
As you can see, the new Japanese vessel is a very large ship. Even at 30,000 tons full load, which is 3,000 tons larger than they admit to, I believe if fully outfitted with aircraft and fuel, it will be closer to 35,000 tons. The Japanese are already building the second vessel in this class.
BTW, in the Sea Control role, the Wasp Class can carry 20+ AV-8B Harrier II aircraft, or ultimately 20+ F-35B Joint Strike Fighters. Given the size of the Japanese vessel, you have to believe it could do something similar if necessary and if the Japanese purchase the aircraft. That would be something to watch for.
As if obamanation would ever sell weapons to a nation that wasn't communist or muslim.
If you look at their Aegis “destroyers”, at full load they are as heavy as our cruisers. Germany and Japan did this before the first World War as a way of getting around the treaty restrictions. Japan could not have battleships so they made carriers and the rest is history.