You guys are forgetting something very important here.. You will NOT be permitted to access the jpn eshop without having a valid SecureInfo_A file from said region in your nand. that file holds your region, serial number (which nintendo keeps on the server) and possibly other important code but this was a necessary step when region changing on a hacked 3ds back about 8 months ago when i tried it, im not sure how different it may be today though so feel free to correct me if this is not the case anymore.