Wakayama To Koyasan & Nachi Falls

Hi, I am thinking of staying in Wakayama for 3 days, and making 2 day-trips to Koyasan & Nachi Falls. Wondering whether this is too rush. Or should i stay in Koyasan or Shirahama instead of Wakayama?
One more qn, is it worth going to Yunomine Onsen?

Thank you!

Koya-san can be done as a day-trip from Wakayama, it's about 2 hrs. by train with a change at Hashimoto. From Osaka it's just 1.5 hr. direct train. You'll miss out a lot if not staying overnight in one of the temples in Koya-san, esp. the memorable walk at dusk in Okuno-in area along the lantern-lit path.

A day-trip to Nachi-no-take waterfalls from Wakayama is stretching a bit too much. It's almost 3 hrs. JR from Wakayama to Katsuura plus another 30 min bus to the Falls, not to mention you'll miss out a lot of interest sights along the way such as Shirahama, Kushimoto and Katsuura itself. We went there this April and spent an afternoon seeing the Falls and Nachi Taisha Shrine. We worked our way down the west coast from Wakayama, spending a night in Shirahama and another in Katsuura before coming back up the east coast of the Kii Peninsula.