So I'm on the 12th floor and I'm really having a problem with the Shining Mirror. This is my first playthrough of the game, and I never played LoT1 before. Now putting that information aside, I noticed that at the beginning of the battle, the mirror is doing basically no damage after I buff up Koma's and Meiling's mind with Reimu's and Keine's defense buffs. In fact, some attacks deal 0 damage. This is when they have about 70%+ Mind. However, I'm not sure if it's when I get the boss to half HP, or after a certain amount of turns, it just suddenly does loads of damage. Even with 100% Mind Koma and Meiling are taking 1000+ damage from it's AoE physical attack, and they're resistant too! And don't forget about the Ancient Curse, oh god. I'm playing at the recommended level too. Any advice that can be given?
(And since this is my first run, I'm pretty sure I've done some stupid things already.)