My wife and I walked the Kumano Kudo before we walked the CF.
We checked out a few commercial trips for ideas and then booked our own trip (at less than 2/3rd the cost), I planned it night by night starting at the smallest towns and confirming accommodation there before booking the rest of the walk.
The Tanabe Tourist Bureau were fantastic, answered my questions overnight and provided such great walking maps (you can also get them at the railway station at the start of the walk if you just turn up).
In hindsight, I should have just outlined my desired walk and let the Tanabe Tourist Bureau work it out rather than going through several stages. Their website is :-
www.tb-kumano.jp
We had a great range of accommodation, from our own house/ traditional japanese hotel/ traditional guesthouse/ converted ex-highschool/ modern hotel. Our hosts were all fantastic and very helpful.
I am a vegetarian and the lengths they went to make dinner and breakfast for a strange requirement in their culture were impressive.
The walk was great, very steep forested hillsides and big river views. Lots of 1,000 year old pilgrim walking evidence and the Japanese survey and manage this trail so well. There are buses at some points if you need to stop early or do short stages. Several big temple sites on the way and the biggest waterfall/temple at the end.
When we walked it was quiet, one or just a few walkers each day and often we were only residents in the facility at night. Walk is very safe, hosts are very supportive and Japanese infrastructure is not so far away if you need it.
This is a culturally rich walk, abandoned compared to the CF of modern times but ringing with history and set in this strange mix of untouched nature and modern Japanese transport.
There are actually three walks (from East, North and West) into the middle and then out to the South that make up the network in this traditional setting. The symbol of the walk is a three legged crow, possibly due to three major clans or perhaps to the three starting points?
We met one Japanese man would does this every year, varies the path he takes. Just in walking clothes, he dons the overnight guest clothes at the traditional stops and has an onsen hot natural bath at each.
We carried too much - based our packs on NZ tramping requirements. You can go much lighter here.
This walk is legendary in Japan but overstated regarding difficulty, many people we met knew about it but thought that two 60 year olds (in not so very fit appearance) had no chance of completing the walk.