Grevil is an aristocrat who had forced the local police to make him a detective purely because he had an interest in crime. The most noticeable thing in his appearance is his drill-like hairstyle that Kazuya thinks could be used as a deadly weapon. Despite being a terrible detective and always having to rely on Victorique to solve his crimes, he usually refuses to acknowledge that she even exists. When he comes to the library he speaks about the case that troubles him to Kazuya, saying that it helps him to clarify his thoughts. Kazuya tries to get him to tell it to Victorique, which he ignores. Victorique tells Kazuya to chat with the detective, that she will just read her books; if she says anything to herself, pay no attention. This is because he is Victorique's half brother and even if they are family they could never acknowledge each other in public. His mother was their father's proper wife and because he is the eldest son he takes all the glory for solving crimes and will take over after their father dies. He is described by Victorique as a heel and a playboy.

Kazuya Kujou is a foreign student at Saint Marguerite Academy, a luxurious boarding school in the Southern European country of Sauville. Originally from Japan, his jet-black hair and dark brown eyes cause his peers to shun him and give him the nickname "Black Reaper," based on a popular urban legend about the traveler who brings death in the spring.
 
On a day like any other, Kujou visits the school's extravagant library in search of ghost stories. However, his focus soon changes as he becomes curious about a golden strand of hair on the stairs. The steps lead him to a large garden and a beautiful doll-like girl known as Victorique de Blois, whose complex and imaginative foresight allows her to predict their futures, now intertwined.
 
With more mysteries quickly developing—including the appearance of a ghost ship and an alchemist with the power of transmutation—Victorique and Kujou, bound by fate and their unique skills, have no choice but to rely on each other. 
(Source: MAL Rewrite)

[Profile](https://osawa-inc.co.jp/men/kiuchihidenobu/)

The year is 1924, the place, Sauville, a small European country neatly tucked beside the Alps... 
Kazuya Kujo has been studying abroad at the prestigious Saint Marguerite Academy, where urban legends and horror stories are all the rage. Most Kazuya ignores -- but the story of the "Queen Berry", a mysterious ghost ship, really gets to him. Of course, his brainy friend Victorique is much more intrigued by true stories, and she uses her unrivaled logic to solve mysteries even the town's famous detective can't. Ironically, it's Victorique's inquisitive nature that leads the duo to board a ship that matches the "Queen Berry"'s description to a tee, a ship that might just hold the key to solving a sinister mystery... 
Kazuki Sakuraba's modern twist on Holmes and Watson-- pairing Victorique, a brittle young girl with doll-like looks with her eager-to-please sidekick Kazuya-- make this international bestseller a must-read murder mystery. 
(Source: Tokyopop)

Kujo Kazuya is studying abroad in Sovuria (a fictional country in Europe), where he meets the mysterious Victoria. Possessing a brilliant mind, which she calls "fountain of wisdom", she seems to know everything, although she never attends classes and is restricted to her room and the schools library. 
 
(Source: taken from the light novel summary) 
 
Note: Volume 2 contains the extra "Suigyo no Majiwari" (水魚の交わり).

Grevil de Blois