Amazon Japan will have a exclusive version of Shin Godzilla featuring a Steelbook case for both the 4K and 3 Disc Blu-ray Sets. It seems from the listing there isn't any difference in the content, 3 or 4 Blu-ray discs, promo sheets, ticket holders, etc. From the image is a sample it does appear to have images on the in and outside, and shows that it can hold 4 discs so it is possible it's the same case for both. Of note it does state that it is region free which means US fans can purchase and play the movie. It will retail for 10,584 yen (approx $90 US) for the 4K, and  8,424 yen (approx $72 US) for the 3 Disc Blu-ray.