Hello! Ideas for birthday weekend

Hello everyone!

I have lived in Japan for about a year now. I have been to Tokyo, Kyoto, Hiroshima, Sapporo, Osaka, Himeji…. but I have four days off for my birthday (public holiday and weekend, yay!)

I am after some ideas for a solo weekend… I love nature, a more relaxing environment, hiking, beaches… I do also like cities but I am not a partier.

Any ideas?

Thank you!

Edit: I live near Okayama!