I almost didn't buy this because it looked like Disney princess dresses, and Ivy's not too fond of princess stuff. But then I started looking through it and the costumes were wonderful. About half were from Western fairytales, and the other half are from Japanese folktales.
I'm not sure what fairytale these characters are from either. It just says King and Grandma
These animal pajamas are called Kigurumi and are very popular in Japan
These characters are from the folktale Momotarou
This is the folktale Urashimatarou.
I'm a little unclear as to what title of the book means, oyuugikai seems to be some sort of School Art Festival and fuku is clothes, so I guess these are just costumes for the festival, which appears to be fairly elaborate from what I found online.