Yes, there's a Post Office on the summit of Mt Fuji. It's tiny... but necessary, because the Japanese are like that. What better moment to send a postcard from some place than the very moment you are there. Plus, postage generally involves stamps, and Japanese people LOOOOOOVE stamps! Add to that the spiritual, mythical and legendary space this mighty volcano occupies in the hearts and minds and lives of the Japanese too, and you'll understand, there simply has to be a Post Office on top.
It was a great day for the climb. I met an Austrian girl on the bus on the way to the bottom, and we ended up walking together. It took several hours up and several down, but the views were awesome, and the people watching was terrific, with lots of people making the journey, most of them locals. You can follow the ridge all the way around the top of the crater too which we did, still quite a bit of snow inside the crater. From the top, you can look out over so much of Japan. It was amazing to be there.