RPGmaker MV, the software which was use to create the game. Allows you to modify the game just as if you were the creator.
RPGmakerMV Decrypter, allows you to access all the files that were encrypt when the game was export to finish state. Gives you access to all pictures and sounds used in the game for exemple.
Paint.net, i used this to edit game pictures, custom outfits i've shown were made this way. Any other soft like photoshop or gimp would do.
Google translate, well it's a japanese game, so everything that the player don't see while playing is still in japanese, map names, switches, variables, events, dev commentary etc....
To mod a game, create a new project in RPGmakerMV, save and exit. Copy all the files from the game you want to mod into the project folder that was just created. Decrypt files and place them in corresponding folders.
Start RPGmakerMV, load project if not done automatically, and you should be able to do whatever you want with it.
It's as easy as that.
