No, you don't need to install anything else.
Because it is a game engine. Game engines are tools, they can't offer something without a developer who knows how to use them. That said, rpg maker is pretty limited compared to unity. This game could've easily been a fully 3d game if it was made using unity but I doubt this dev knows how to use it.
Eh. Most 3D Unity Hentai games are shit. It most likely would have lost some of it's charm.
3D is a downgrade 99% of the time. And 100% of the time when your artist only does 2d work.
It would definitely lose atleast some of its charm. But I just wonder how it would look and play. I am imagining something like last evil but without cards and with better graphics.
Like I said. Personally for me, I hate the cartoony look of these 3D Unity Hentai games. Last Evil has kinda shit looking visuals. Much much less quality then the hand drawn art KP has.
Im not telling to make 3d , but you can use live 2d things like samurai vandalism, but like i said its no going to happen
Idk what you mean by assets but most if not all of the code is already in a readable format. Pictures can already be extracted/converted from game files. Same can also be said for sounds effects and voices.
