I think I have a better explanation: he's 82 years old. If he's not in exceptionally good shape, the job of a formal head of state may be too much even in smooth times.

Japan has been printing money and economy has tanked for 35 years, but still life is good for the Japanese.

A war with who?

Haven't read much about Japan. But I'm quite sure that China is looking for someone to make a war with and they still have some grudges with Japan. If Japan on the other side is also heading in the direction of war there may really something happen. That's worrysome.

Nobody wants war in Asia. The question is how and at what rate the United States withdraws from its ultimately unsustainable position as pacific hegemon. China would like it to happen sooner. Most of the rest of Asia would like it to happen later, and to share more equitably in a post-american security coalition. To make that possible, Japan and South Korea may need to show more strategic solidarity in the short term.

If you only look at the public evidence you are right. If you get to drunken politics discussions with Chinese men at 3am at night, then it looks a little different.