The game is also made on using version 1.3.1 of RPG Maker MV, which have a massive memory leak. The game eats an additional 100~200mb of RAM every time you open the game menu. Just opening the game menu 10 times will make the game eat an additional 1gb of ram. You have to apply this patch:
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I'm not sure if its working though since it is still eating gigs of ram after a few minutes when I tried. I think I applied the patch wrong. (I copied it to the plugins directory.)