Day Hikes in December

Are there any mountains in Japan that can be hike (day hike) during December?

Thanks in advance.

Yes.

I would think that at a minimum Takaosan in Tokyo is available, but there should be many more, lower mountains in the South or pacific side of Japan that are hikable in December. Mountains in Tohoku and Chubu (as well as Hokkaido) are likely covered in snow, as is Fujisan.

Where in Japan are you visiting?

Japan covers a big difference in elevations and latitude so this makes a big difference

I recommend this page as a starting point for your research:
https://www.japan-guide.com/e/e2427.html

It lists whether the paths are open around the year or not (although some of them come with a chance of snow).

Thank you for all the tips. I'm probably going to do the 5 Shrines Trail in Togakushi and Kiso Valley. I heard their open in December.