So...
I was searching the same, didn't found any save in this page, but then I checked the img folder the game has:
and there I found a gallery save.
It does the trick pretty well.
Pretty sure you should have that folder, "全開放セーブデータ". There should be a SaveData.es3, which you place/replace it on "喰牢の牙_Data", and good to go.
Go to "img", then "全開放セーブデータ", copy the SaveData, back to the main folder, "喰牢の牙_Data", and paste.
Cheers!