I own this on the Vita, and I will cheerfully buy it again should it become available here. Heck, I bought the first game on steam (and they had to release it as an adult game, despite it NOT being one) and I would re-buy it here if it would help get them all available.
It is a very solid dungeon crawler that has the misfortune of also having an anime art style with the occasional bikini/panty shot, which means that OF COURSE steam had to ban it.
The game hits all the needed notes with dungeon crawlers, with the addition of really needing to balance your team, farm monsters for boosts, and pick the right character upgrades. Couple that with a good voice cast and there's a winner.
The only place it is available on PC in English has the most regressive DRM I have ever seen (three installs and you rebuy? Seriously?).
Scuttlebutt among fans suggests that Aquaplus (the JP publisher) vetoed anything but steam, so someone at GoG would need to talk to them to confirm that. It is already translated and available, just not in an acceptable form.