I finished this game 100%, got three endings and the special scene.
Here's my game-breaking tip:
Don't leave the first level. Just do a few bosses, let the last one beat you and restart the level while keeping all your skills. Rinse and repeat.
Each boss on the first level gives you a massive stat boost, it does not take long to max out all stats. Each monster gives you the same stat each time, so you'll soon figure out which monsters you need to fight to max a certain stat.
You can't really tell how much HP or MP you have so just upgrade that a bunch of times. Once your stats have maxed you will roll over every monster you see, except for that one battle you cannot win.
1: Lose to the Dragoness after level 2.
2. Beat the Dragoness.
3. Beat every non-monster in the dungeon. You've got the Witch, the Thief, the Angel, the Elf and the Warrior.
Once you have 100% of every CG the main menu will contain a bonus scene.
Short walkthrough, but it's a short game. I'd like to know what was being said but I doubt a tiny game like this will get translated. I would rewrite it myself if I had any idea how