I also got an error after the first battle.
I have a feeling that the game doesn't really connect to a server until after this battle and, when it attempts to, it crashes.
I must say, this isn't bad so far. Keep working on it.
It really needs to be worked on, but it's not bad.
You need a stable and/or online server.
You should improve the battle system so that Leer and such actually lower stats.
This game has potential and if you keep working on it it'll get better.