The case, presumably designed for the Nintendo Switch, features the 6 characters from the box art on the front and the Chinese Fire Emblem Warriors logo on the back. Note that the final design may vary.
A full list of participating retailers offering this pre-order bonus can be found on this page. As usual, supplies are limited and given out on a first come, first serve basis. (If in doubt, be sure to ask the retailer.)
In any case, Warriors will release in Hong Kong on the same day as in Japan: 28th September 2017. As we reported earlier in the year, the game will be the second Fire Emblem title (after Echoes) to receive an official Chinese translation.