Well, the fact is, just like with China, unless the buy some STOVL aircraft from somewhere all they can carry are helicopters.DDH??? What a joke. If the Japanese believe lying about their LHAs by calling them "Helicopter Destroyers" would make their neighbors less concerned about their aggressive postures, they're out of their f-ing minds.
There is no ski-jump, and there are not cats. And the hull is not designed for either. Unless they come up with some Harriers (which they will not...too old) or some F-35Bs, all they will carry are helicopters.
If the Japanese fund and begin talking with the US about buying F-35Bs, then you will know what their intent is. Until then, by default, they are helicopter carriers.