Save files are in AppData\Local\futanari_modification. It's all plaintext with each line a different (unlabeled) value. Editing your money or mana should be as easy as finding the numbers and changing them (the files aren't very big). Other things basically require knowing from the source code what lines mean what. If you were looking to change something specific, I could try to find the line number for you.
As an aside, I have actually been on-and-off making additional changes to my copy of the game, mostly graphical updates and bugfixes, but some gameplay changes too. At this point it's more of a full mod than just a translation. If I ever get all the kinks worked out, I may post it here. Or maybe I'll make a new thread, who knows.