I've been using Buyee for the past couple of months now, and it is a super helpful proxy for overseas customers. Their fees are pretty transparent and can compete against other Japanese proxies out there. The entire process is a little less than straightforward if you don't read everything up front, but they do spell it out in their other pages for those that read. The nice thing is that they've started offering more promotions for free international shipping or free proxy fees since they took feedback about how it was expensive. They offer a wide variety of shipping options, along with package consolidation services, which is super helpful. I've bought many items from Mercari JPN, which has official affiliation with Buyee. Because it is a proxy, that means Buyee acts as a middleman to buy things from the Japanese sites on your behalf, and therefore, it can take 1-2 business days to process and secure your order for Mercari.