Dantalian no Shoka

Synopsis

In Book of Wisdom: Huey and Dalian visit a local bookstore, and are bickering with each other when they run into Camilla, an old friend of Huey's. She invites them to her villa for tea, and tells them of a friend who had opened a school to compete with the one she was running, and had claimed to have gotten hold of a Phantom Book that made her children smarter when they read it. However, the children reportedly became too smart for the teacher, and seemed to have taken on completely different personalities. Huey and Dalian arrive at the schoolhouse to investigate. In Queen of the Night: Huey finds Dalian tending to a rare African cactus in their greenhouse, which is said to bloom only one night every thirteen years. Suddenly, two burglars break into the house and take them hostage, in search of a valuable book called Queen of the Night.

(Source: Wikipedia)