Onikakushi is free. Also, the absolute achievement rate is a bad metric, you need to look at last achievement rate by first achievement rate. That number for Onikakushi isn't all that high either (30%), but the numbers for the paid chapters are higher (76, 82, 95 but it's short, 87, 88, 86, 74). The 6th chapter is where the first achievement rate jumps from 40% to 70%, which is probably related to sale patterns more than anything.
Yeah, figured. Maybe I just really shouldn't be all that surprised that the anime and manga have better exposure here. It's only been relatively recent that the sound novel has become more-widely available, but visual novels in general are more niche here. But one would think Higurashi fans would chomp at the bit for a chance to play through the original because it's such a fascinating look into the mind of paranoia.
I bought 1-7 on GOG before 8 was released, finished them all, and I'm not going to play 8. Two of the four tolerable characters got done dirty by subsequent chapters and the plot is a scam (there's no answer to 3). I'm gonna stick with whatever positive impressions (chiefly from 3 and 5) I still have.
That's a shame. I consider Massacre and Festival Accompanying to be the Curse Killing's answer arcs given just how crucial Curse Killing was to solving the mystery of the curse, even though it was the (true) ending of Atonement that laid out all the theories. Festival Accompanying is also needed to understand why Outbreak (an optional watch) was so fucked up.
I wonder if the Dice Killing chapter will get a proper release, though. It's not really needed for the full story, but it's still a fun look into that "what if" scenario of Hinamizawa succumbing to its dam fate. Though it's supposedly not as sad of a world as those where Keiichi never showed, which we haven't seen.