Gosick is a Japanese light novel series by Kazuki Sakuraba, published by Fujimi Shobo. Set in a fictional European country in 1924, it has as main characters two young students named Victorique and Kazuya.

Victorique is a mysterious, brilliant girl who only leaves the library to sleep. Small for her age and hidden from the outside world by her family since birth, Victorique is physically and emotionally as small and fragile as her brain is huge and complex. Rumor also has it that her mother is insane and that her family is afraid of her as well.
As the third son of an Imperial soldier of Japan, Kazuya has always lived in the shadow of his father and his brothers, questioning if he will ever have enough strength and muster to protect anyone.

Kazuya relies on Victorique's mind to solve difficult mysteries, several of which draw her away from the library.
Normally, Victorique and Kazuya go to a private ultra-elite school, Saint Marguerite Academy. But the two get involved in several adventures and they get out of trouble with the help of Victorique's great intelligence.

Even if Victorique is the brains of the action, Kazuya has to keep both of them alive long enough to solve the mysteries and present the solution to the authorities.