Hi, most comments are probably towards RPG Maker here. But since you asked this in VN Maker Sub-Forum, in VN Maker however, if you select Game > Create Game Package there is check box "Encrypt Content" which will encrypt your assets so they cannot be opened/seen/edited anymore. However, Video Assets cannot be encrypted. I think in RPG Maker it is similar.
However, as others already have mentioned, no encryption is really safe. Encryptions can be figured out by hackers and then shared with everyone. People can also steals assets just by doing screenshots of your running game or recording the music.
The thing about encryption is more that no one can super easily get your assets by simply browse the folder and copy-paste everything and also to fulfill certain license agreements forcing you to encrypt your assets. But if someone really wants to get your assets, that person will find some way.
But even then, if someone tries to sell a game with stolen assets in a Store like Steam, if you can verify you are the true author you can force them to take the game down quickly I think.
Hope that helps.