As others have said, watch this at least after ep12 of the main show. This is a prequel story from Chise's childhood. It starts out slow, but we get all the mystery and emotion from the main series here as well. There's not much to say here. During the first episode I felt it was quite a bit too slow, and even during the second I was interested, but still waiting for something to happen. The last episode cinched it though, and I get the climax I wanted for this kind of story. It's not required watching, but if you enjoy the main series I for surerecommend watching this as well.