Japanese devs seem to be able to put out finished/semi finished games based on RPG Maker (primarily) and Ren'Py (occasionally) every few months with art (usually character stills), animations (pixel animations or 3D based) and roughly the same amount of text as this game (yes, the whole game), as well as the same rehashed combat system that everyone does.
But somehow almost all of these Twine western games are stuck in development limbo (to say it lightly, because the scamming accusations are getting repetitive). I guess japanese devs have special courses to make lewd games and they have a framework and teams with years of experience...
...or maybe, I dunno, the fact that they only get money once they release it and it's sold is a good incentive.