Sunny Milk is the fairy of sunlight. She often hangs out with Luna Child and Star Sapphire, and is the de facto leader of the three. Whenever they do something together, she stands at the forefront, which makes her an indispensable member of the team.
Luna Child is the fairy of moonlight. With her ability to mute sound on your side, it's possible to play pranks without making any noise. She is an indispensable member of the team.
Star Sapphire is the fairy of starlight. She lives together with Sunny Milk and Luna Child in the mongolian oak tree behind Hakurei Shrine. She's in charge of cooking for the three fairies, which makes her an indispensable member of the team.
The three fairies secretly participated in Remilia and Rumia's Trick or Bullet prank festival held in the Human Village. The children shout "Trick or Treat!" to show the spirits of their ancestors that they are healthy and well. Seeing this, the three fairies think up a plan...
History of the outside world was written in one of Suzunaan's books from the outside. It detailed the special event where people wear costumes and walk around receiving candy. This was apparently where the idea for the prank festival came from. As chance had it, Koakuma read out a book to the fairies by the Misty Lake which talked about the same thing. The three fairies misunderstood the story and thought it was a festival for fairies!