Luggage and the Fuji rock fest

Hullo all~
I'm a Brit who will be travelling in Japan for two months this summer, the first month travelling from city to city and staying in hostels, the second renting a guest house in Tokyo.

I've just booked myself some tickets to the Fuji Fest, and as I'll be camping I'm wondering what to do with my luggage, I'll be taking a fairly big and heavy bag with me and I'd like to leave it somewhere and just bring a backpack with the essentials for the festival weekend. Can I trust that there'll be locker space in Echigo-Yuzawa Station for a big bag, and that I'd be able to safely leave it there the whole weekend? Is it likely that I'd be able to leave it at a hotel or hostel even if I'm not staying there?

I know it's quite an obscure question but I just don't want to be stuck (literally) in the mud with a bag that I'd be nervous to leave in a tent.

Thanks a lot!

It is likely that you'd be able to leave it at a hotel or hostel that you are staying right after camping at the festival. So book a place and ask them. It's not an obscure question.