One entry: a Greek temple on a canal in Okayama, which has no business existing and is all the better for it.
Late autumn, and I would not go in high summer.
It is a long way from anywhere and the trains are the price of admission. I went in late autumn, which I would repeat: the light on the canal is low by mid-afternoon and the day-trip coaches have gone by then.
Do not treat the annexes as filler. The craft wing — Hamada, Kawai, Leach — is the part I think about most, and it is the part everyone walks past on the way to the paintings. Give it a proper hour rather than the fifteen minutes it usually gets.
The town is small enough that the museum is the plan and everything else is what happens around it. That is an honest description, not a complaint; one very good building and a canal is a better day than four indifferent ones.