Is there a particular reason you don't give the game name (I assume VN is visual novel as well).
Visual novels in my experience, even as late as the PSP, can be anything from glorified slideshow (in which case you are more likely to be editing images than playing with tables) to more general game to straight up internal scripting language, usually trending more towards general game like most of what we deal with around here for the PSP (the slideshow stuff tending to be older budget games on the PC as it is a limiting way to make games).
Even without that then having a translation (I presume this is the classic someone transcribed it on gamefaqs or similar type deal) in a more plain form is seldom ideal for hacking, even more so if you end up having to change things to fit within the game
What have you tried? Decryption is a specific thing and does not necessarily apply to PSP games today (back when various binaries might have had to be decrypted to run but today all the keys are known). Indeed outside of the PC and a few cheats and saves encryption is not really a problem ROM hackers face, at least by the time most people are considering translating games.
Have you pulled the game apart with umdgen or something and seen what files it contains (including file names, sizes, directory names)? Maybe tried swapping them around a bit to see what changes in the game?