Oze National Park via Nikko

A friend and I are considering going north to explore Nikko and Oze National Park for a few days later this month.(Hopefully there will be snow!). What's the best way to get from Nikko to Oze?

Secondly, what kind of day hikes(under 10 hours) are there in Nikko? Most of the info I've found is on the shrines, and we aren't terribly interested in the shrines.

Do you think it might be best to do the two parks in separate trips? We'll only have 3 days.

What's the best way to get from Nikko to Oze?

There is a direct road, but no public transportation. You will have to travel by rental car:
http://www.japan-guide.com/e/e2024.html

If you don't drive, it will be a huge, time-consuming detour via a southern route. Either by shinkansen via Omiya or the JR Ryomo Line.

Secondly, what kind of day hikes(under 10 hours) are there in Nikko?

I recommend to hike around the Senjogahara and Odashirogahara Marshlands. For example, from Lake Yunoko to Chuzenjiko:
http://www.japan-guide.com/e/e3811.html

Note also that it is very much towards the end of the hiking season, and there is a risk of snow already.

This is even more true for Oze. I am not sure whether it still possible to hike there now and even more so later this month.

About Oze:
http://www.japan-guide.com/e/e7440.html

I don't know exactly when they officially close for the winter, but the public facilities there, including toilets and mountain huts, are already closed (early ones in late Oct., the last to close is just around now) according to this website:

http://www.oze-fnd.or.jp/