I'm not sure, but I played that spot again and it didn't happen, so I'm good there. Though, in the under-the-school area, there's an enemy with no sprite...It can Berserk people, if that helps you ID it. Also, in Momiji's area(Just started controlling her), the enemies I was fighting had no sprites either... They had Escape and Double attack, I know that much. However, I couldn't tell you WHAT they were since they were invisible. Look into it, perhaps? Also, I got some error the first time I tried entering a battle there that killed the game. I had saved, luckily, right after fighting that interesting Keine battle and Tenshi, so I didn't lose any progress, but still.
Also, Tengu Mountain signs = broken? I try to read them, but nothing.