Where to get a 2 / 3m cardboard box?

Hi there!

When I came to Japan I came with 3 boxes of clothing and shoes, but a combination of corona, remote work and buying new stuff here resulted in not using even the half of everything I brought, actually the collection grew a little bit more..

So, now that the apartment contract finishes in a couple of months and I’m planning to visit the family for christmas, I thought it would be a pain in the ass to just send everything to the new place since most likely I’m not going to use it, and thought that rather than sending 2 or 3 boxes back to my country, would be better just sending a huge one whether if it’s totally full or not.

Japan Post international parcel cardboard length is up to 2m or 3m depending the country, being the longest side up to 1,5m, but checking in Amazon the biggest size I could find was enough for a guitar.

So do anyone knows where can I find a cardboard box big enough like a washing machine or fridge? lol

Thanks in advance.