I agree with Reaper, you need download and read walkthrough.
Boss in Spire of Courage you mean Shika and Funeral? I recommended you complete Chiyo "Gold License" quest first before challenge them.
Craft Water Katana and Water Dagger, give it to Tsubaki and Sandra, use that weapons to fight Shika and Funeral.
Don't forget to defeat all fairy's and collect water bottle and water bucket. Use Sandra Pickpocket skill to increase number water bucket you collect. That bottle and bucket can be used to remove burning effect.