Descendants of darkness - Yoko Matsushita

When you work for the Ministry of Hades you have to be ready for anything, even on vacation. While on their annual retreat to a Hokkaido hot springs resort, Asato Tsuzuki and company meet a pack of talking animals who serve the Queen of Snow. But now the Queen is missing and there's a vicious dragon prowling nearby. Can Tsuzuki and Hisoka find the Queen before she becomes lunch - or something worse?

In another case, Tsuzuki and Hisoka must investigate a 17-year-old who's been murdered and his body mutilated. The investigation takes the two Guardians of Death to a private boys' school where they discover that other boys have died. Soon, they're deep into the dark and bloody secret haunting the school.