Hello. Thank you for taking the time to try the demo. The project is not developed on RMVX but on 2003, without patches or plugins (Event making). This version is starting to get a bit old; many things didn't work as I expected. The next version will be more balanced and will fundamentally change the gameplay.
I made a tutorial a while ago explaining the basic principle. Sorry, it's only in French :
Part 1 : https://www.rpg-maker.fr/index.php?page=tutoriels&id=699
Part 2 : https://www.rpg-maker.fr/index.php?page=tutoriels&id=700