Having been stationed on a ship homeported in Yokosuka, I can say that I've visited the Mikasa several times. And unfortunately, there isn't really a whole lot to see in the the old girl - even though everything is pretty well maintained, the sad fact is that it is because there's pretty much not much to maintain. Most of everything is gone, and nothing below the water line is accessible.

The only things of real interest left is the officers quarters and ward room in the aft of the ship, because all the accoutrements and furnishings were left in place and preserved, thus giving one an idea of what a line officer's existence in the Imperial Navy of the time was like. There's also an animatronic diorama that displays the battle where Admiral Togo came up with the Togo Turn.

It's really quite a let down, and personally I blame the USA for her treatment. A ship with such a history as this one deserves to be preserved the same way we've preserved the USS Constitution, but in our anger and righteous indignation, we wouldn't permit that.