We will be spending 2 days in Yoshino and then have 2 nights before returning to Osaka. Looking for suggestions and transportation info on getting from Yoshino to a village with trailheads for doing shorter hikes within the Kumano Koda/Kii Peninsula network. We will have a JR train pass but it seems we may need to take a bus or two as well.

Do these help?
Tanabe City Kumano Tourism Bureau: Kumano Kodo, Onsen, Traditional Cuisine and Spiritual Culture
https://www.japan-guide.com/e/e4952.html

Evidently no service in the winter...don't know when you plan to go....

Kintetsu train to Tennoji then JR to Kiitanabe or on to Shingu.
Your departure station for hyperdia.com is YOSHINO(NARA)

Or Kintetsu to Yoshinoguchi then JR Wakayama Line to Gojo or Hashimoto. Then bus.

You need to get a train to KiiTannabe, and from there it's a bus to wherever you choose to walk the Kumano Kodo from.

The website Kumano Kodo | has all the information you need, and they are really helpful.

I'm walking the Nakahechi route from Takijiri-Oji starting on March 19th. All my accommodation is booked (and you really do need to reserve ahead) and also my luggage transfers. I am looking forward to walking this trail and because I have already walked the Camino de Santiago becoming a Dual Pilgrim.