I managed to digitally purchase the volumes but can somebody (who can read Japanese) please provide a detailed purchasing guide for those outside of Japan. The kobo.com link did not allow me to purchase the volumes so I had to go through rakuten.co.jp and find the volumes there, but it turns out there are two separate purchasing flows, one of which required a (japanese?) phone number I couldn't get past and another that went through WorldShopping that actually worked. I don't feel qualified to provide this guide because I was basically clicking around blind.
Yeah, I think there was some policy change at Kobo, so even though I've been buying my raw manga there for a few years there, I can't recommend it anymore for that. BookWalker is the easier route if you don't have a Japanese address and phone number.