The story is told by Kai. He tells that as he was about to be born, his grandmother made his parents say a prayer for the child's health. When Kai is born, his sister Toshi unexpectedly is born with him. The twins are happy as children, and one day when they are playing, Toshi jumps out of her treehouse but discovers that she has immunity against injury. Soon after Kai discovers that he can't be injured either. Strange occurrences continue, as the twins and their friend discover magical fantasy world through the Sanno Shrine. There they meet the god of swords, and things take a turn for the worse over 3 volumes.
Tropes related to the series:
- Author Appeal: Carey really loves a lot of J-Horror and manga, but also when telling about the kids' childhoods he mentions a lot of his old favorite anime like Arsène Lupin and Gundam.
- Bratty Teenage Daughter: Toshi. Kai thinks to himself that because she can't feel physical pain, she tries to find other ways to be in pain so she can feel human.
- High-Pressure Blood: That's a lot of blood for a dog...
- I Know Your True Name
- Kick the Dog: Or, brutally murder the dog.
- Made of Iron: Kai
- Meaningful Name: Toshi, "mirror". And Kai is the reflection.
- Nigh-Invulnerability: Toshi, first discovered when she jumps from the treehouse and doesn't get impaled by the wrought iron fence.
- Razor Wind: Aratsu, god of knives, literally does this. He controls a tornado of wind with knives flying through it.
- Shout-Out: To many different anime from the author's childhood, and different Japanese horror movies.
- Treehouse of Fun