In 1980, a Japanese man met Masako Natsume in Kamakura, and she gave him her autograph. See the The Day Keisuke Met Tripitaka! page for full details.
Here's the autograph - click on the image to see a larger version of it:
This image has been copied from the following web page:
Back to the Monkey Autographs - Masako Natsume page