How do you unlock the cg gallery?

Howdy, to get straight to the point. I have kansen (5)? And this games all about the decision making and right or wrong choices. Anyways, I'm searching for a way to unlock the gallery because im on literally 25th playthrough and cant seem to find any other routes. As well as i cant read moonspeak. It shows the save data sys data and all that in the directory, but i was just wondering if there was a trick to unlocking a games cg by like opening a certain file and changing a variable or what have you, and as to whether its a trick that can be used in all VN's in general.