How to forward luggage to Kii-Katsuura?

Next year in May I will walk part of Kumano Kodo. Arriving at Kansai Airport I don't want to bring my larger bag with me. There are luggage shuttles along the Kumano route, but apparently only if you book all you accommodation through Kumano Travel.

What is the best option to forward luggage to Kii-Katsuura? Either from the airport or Kii-Tanabe.
I will pick it up 4 or 5 days later.
I read it is possible to forward luggage from convenience store to another convenience store. But will they store it for that long?
Is it also an option to send it to Kii-Katsuura station?
I hope someone can help me.
Thank you.

You can send your luggage to your next hotel or to a office of the transport company. I havenft heard of sending luggage to a conbini, but maybe thatfs possible. To a train station I donft think so.
The luggage holding happens at the shipping company. When you ship your luggage you fill in the date when it shall be delivered. They can hold onto the luggage I think for maximum 1 week. If you ship to a hotel make sure they know you are coming.

If you don't mind storing your luggage at Kansai Airport, there are few options:
(1) coin lockers at Nankai Railways station of Kansai Airport stores up to 10 days;
(2) there is a luggage storage/forwarding vendor "nEeEsEt" that stores or forwards luggage (not sure if forwarding is limited to Osaka and Kyoto).

Ref site, in Japanese: https://www.nankai.co.jp/traffic/kix/kix_station.html
It says they are currently closed due to the pandemic, but I'm sure that can change by the time you travel.

Are you staying in a hotel somewhere after your walk?if so, send the luggage directly to that hotel while you are still at the airport.

https://www.kansai-airport.or.jp/en/service/delivery

KIX is not a convenient airport so I wouldnft recommend storing your luggage there. Just get it delivered to your hotel.
Specify the name of the hotel (show the delivery company the screenshot), date of arrival/ Checkin date, and your name.
Most hotels will hold them & therefs no need to contact them if you have a reservation.
Generally, delivery company will hold it free for 7 days.

I believe the Kumano Travel Bureau can organise luggage transfers for a fee. Similarly, they can also book your stay at the different guest-houses which are located in small villages along the Kumano Kodo Nakahechi route.

Best of luck,