Apparently some files are missing or renamed, couldn't proceed with the first encounter in episode one, the game gave me an error that GustavBattle.png is missing. I copied Gustav.rpgmvp, and pasted a new file under a name GustavBattle.rpgmvp back in www\img\sv_actors folder and it worked. So if anyone encounter something like this later in a game, try to do like I did.
Edit 1: in the same encounter with the werewolf there was another file missing, this time it's ClawSpecial2.png. There is a file named ClawAnimation2.rpgmvp in the folder where the error told the file should be, so I copy-pasted and renamed it to ClawSpecial2.rpgmvp, made the game work again. I am starting to think that either the dev has renamed the abilities and sprites in the later versions and forgot he used them under different names in the past ones or he doesn't test the game after updates at all. Did anyone else encounter such problems?