Invalid image size. The longer side of the image must be at least %d pixels long. For more details, see http://sellercentral.amazon.co.jp/gp/help/25631
The image you specified does not meet the minimum requirement for length on the longest side. Images must meet a minimum size requirement. Otherwise, they cannot be effectively resized for various uses on Amazon.com. Please resubmit your inventory file or product image data feed and reference an image that meets the minimum requirements indicated in the error message.