As pointed out by yoohiyy、Crystaltimes introduced in the link above was an American site。Actually, the American site is for the United States only and does not ship to Japan。
I'm very sorry (sweat)
Currently the active site we can order is in the UKHere ↓is。
https://www.seikomods.com/shop/ct715-skx013-to-mini-turtle-conversion-case-crown-at-4/