Takachiho Evening Kagura - you need to commit to this one. We're talking lining up an hour early just to snag decent seats, because this place fills up fast. While it's an incredible piece of living history, with masked dancers bringing ancient Japanese myths to life, it wasn't exactly a hit with the kids (there's only so long they can sit still watching traditional dance).
We took a bit of a risk staying late for the performance and driving back to Beppu in the dark, but sometimes you've got to do what you've got to do for these cultural experiences. Happy to say we did it. You should do it only if you're very into these kinds of things.