I've used Zenmarket about like 6 times and i've gotta say they are pretty straight forward with the payment systems and the 300 yen fee.The only real downside is often they just deduct the shipping within japan(from the seller to the warehouse) with out any real confirmation... like its not a huge deal but often sellers on yahoo auctions give this vague estimate for how much it'll be. So i recommend adding about $5-$15 extra when you wanna purchase an item via yahoo auctions japan just to be safe ( they do have the net of credit if u don't really care so that's really nice)