Buyee

I LOVE Mercari.jp because they have such a wide variety of items that beats fril.jp hands down, the only drawback... Mercari sellers can be a bit choosy when it comes to buyers so I have to go through a proxy to get my sweet sailor moon merch or sarasa clip supplies. In Comes Buyee. (* v *)b
Buyee allows me to purchase ALMOST anything but I have to use their service at certain times of the day to make sure the item I selected gets bought successfully before someone else grabs it, time zones make a big difference because Mercari.jp is a japanese app and I don't have the advantage of just buying something without Buyee's help.
Buyee has a really great customer service team, if I have inquires, I simply shoot an email and I get a response that night which is fantastic.
For example: I wanted to purchase a few sarasa refills but the seller included a perfume in the set, I was devastated because perfume contains alcohol and thus cannot be shipped via buyee's guidelines. But one quick zip of an email with a suggestion about removing the perfume worked out in my favor, the buyee customer service team were quick to help and happy ending I got to buy my refills.
I like Buyee's constant promotions but truth be told I really miss the FREE SHIPPING coupons they used to give out, 500 yen is not enough when the order is past $100. I'll keep saying it until I log in and see that shiny beautiful FREE INTERNATIONAL SHIPPING COUPON, other than that I also miss the free service fee coupon too. I like to save money so buying cheap items is great but when you take on 500 yen to a 300 yen item it can be a bitter sweet buy at times (I still make the purchase if I really want the item though).
Anyways, All in all Buyee is a great service to use (when their behaving) they have excellent coupons and the customer service is a breath of fresh air with how polite and quick they respond to questions or any other concerns you might have. Just be mindful of the 500 yen service fee, when you shop with that in mind, it makes things easier trust me.
I totally recommend Buyee.

I have been using Buyee for approximately a year now, and have purchased multiple items through them from Yahoo Auctions, Mercari and Rakuten. My experiences are mostly positive, though there are things I really don't like about them.

What I find positive:
- (main reason :) ) through them I have access to items I cannot find elsewhere, or I can only find them for several times the price
- the site's built-in translation function makes it easy to know what you are purchasing
- there are at least 5 different shipping methods available, from SAL to EMS, depending on the level of tracking and protection you need
- the 30-day free storage period lets you purchase several items, and then consolidate them into one package
- during consolidation, individual packages are not opened up, they are just packed into a bigger box - some people don't like this (this makes the package bigger), but I *strongly* prefer this approach - this way I can be sure nothing gets lost or damaged during careless repackaging
- coupons and free fee offers are available often, through which you can save some money. Their 11.11 offers on Mercari were especially good (though not so good on Yahoo! JAPAN Auction)
- customer service has been helpful for me everytime I had to contact them

What I don't like:
- fees are unreasonably high, it is often not worth purchasing smaller/cheaper items because of them (for example, the minimum fee on Yahoo! JAPAN Auction auctions, without any protection or extra service, is 500 Yen - approx. 5 USD)
- on Yahoo! JAPAN Auction, fees have to be paid separately for each item bought - even if they are from the same seller, and even if the seller bundles the items. It would be nice if buyers could at least combine purchases made from the same seller
- offers and coupons are often offered only for high-value items, especially on Yahoo! JAPAN Auction (e.g.: coupons are valid for items above 10,000 YEN - way too expensive for me, I never buy items within this price range), so even though the site says they have offers often, I cannot take advantage of most of these... Luckily, offers on Mercari are usually better (no or lower minimum price required)
- the system that automatically determines prohibited items (that you are not allowed to buy) isn't really good. I have seen non-prohibited items marked as prohibited several times. You can ask customer service to review these, but sometimes they still remain incorrectly unavailable (or while customer service gets to your request, someone else buys the item...)
- sellers have a high authority, and it often happens that you are not allowed to purchase an item - or the seller cancels the purchase after you've paid for it. You get your money back automatically in these cases, but it's still very frustrating!