Many Japanese sellers on Ebay deal in volume, some don't have the item they have listed in hand (by design, not to be deceptive), so bags from Japanese sellers in terms of condition is like a box of chocolates.
As for authenticity, there are some like ELady or Yuko or others who have been caught selling fakes, although never intentionally; when you are moving thousands of items then things are bound to slip through the cracks. (I've noticed in the past, that they do have a mind-boggling level of stubbornness when it comes to their own perceived invincibility or immunity to stocking/listing fakes; many times when I've politely sent them a message notifying them, rather than looking into the issue they have flat out denied. I do believe they were sincere in their denial although that does not change the end result. I do think though that part of this is probably because they are also used to being falsely accused of listing fakes when their item is authentic but uncommon, vintage, etc., and so any query resembling that they perceive to be simple ignorance. I would not be surprised if, when presented with the notion of counterfeit or on the receiving end of a VALID counterfeit Ebay claim, they just silently accept the item back and chalk it up to buyer ignorance whilst believing that the buyer is still mistaken and not them).
Because of the mass volume of items they sell, it's become no longer reliable to gauge the quality of a product by the seller's identity (meaning, if I buy from X, will I get a good product). Especially for sellers who don't have the item in hand and they are listing on behalf of other brick and mortar stores, the entity listing the item just goes by the attributes that are communicated to them from the shop and things can get lost in the shuffle or not mentioned. You need to judge each and every single piece individually; this being said, buying a fake from a Japanese seller is very rare (although does happen), you are more likely to get surprises on the condition-related end, but again you may also be delightfully surprised by good condition too. I bet every single customer has a totally different experience with the same seller just because of their sheer volume.
So I'd go with someone who takes returns, at least then you don't have to wait for Ebay to step in if something unexpected occurs.