The last few years have shown that Square Enix is devoted to the PC, releasing nearly the entire Final Fantasy back catalog and new JRPGs like Final Fantasy 15 and Dragon Quest 11 that would've once been console exclusives. Now, in what may be a sign that Japan's PC audience is growing, Square Enix is taking a first step: releasing a game on Steam exclusively in Japanese, without it being region-locked to Japan. SaGa Scarlet Grace is launching on Steam on August 1st, side-by-side with its console versions.
As pointed out by Resetera, this is a new move for Square Enix, and SaGa Scarlet Grace is probably a good game to test the waters with. The SaGa series is infamously complex, borderline impenetrable, and several of its entries and remakes have never been released in the West. There's also a PC connection: the browser-based Imperial SaGa, also only available in Japanese, came out a few years ago.
In this case, it seems likely SaGa Scarlet Grace will get an English localization on PC, which may be why it's not region-locked to the Japanese store like some other games. Series creator Akitoshi Kawazu confirmed an English version was underway back in April, but it still has no planned release date. So for now, Scarlet Grace will serve as an interesting test case for how well Japanese RPGs can do on PC in their home region.
Square Enix isn't the only Japanese developer to release games on Steam without English translations. Koei Tecmo has been doing so for years, releasing ports from its back catalog like Nobunaga's Ambition and Uncharted Waters. We'll see if this is a one-off for Square, or the start of a trend.