Japan in one week

Hubby and I have only ONE week in Japan in mid-March. The more research we do the more we want to see, but need help on prioritizing. TOP on our list:
TOKYO, KYOTO and TAKAYAMA.
We want to have an ONSEN experience and really wanted to see HIMEJII or HIKONE castles. We like to walk cities and explore villages, therefore, the idea of the post walk between TSUMAGO and MAGOME seemed so neat. You see, we are overwhelmed and need some realistic experienced points and suggestions. Thank you so much!

One week is not a lot of time. Especially if you like a slow pace of travel and have never been to Japan before, I recommend to visit only Tokyo and Kyoto.

If you like a fast paced travel, you could also pack in Takayama, where some accommodations have hot spring baths. But I am afraid that packing more than that into a single week would make the trip very rushed.