A well known detective in Saubure, and Victorique's half brother.
Grevil is a member of the De Blois Royal Family, and a well known detective throughout Saubure, despite being quite terrible at it, with many of his cases actually being solved by Victorique. However, since Victorique is his Illegitimate sister, he is unable to acknowledge their relationship, particularly in public. despite this, he does personally acknowledge her, initially being cold and formal, but eventually warming up to her.
Grevil is most noted for his unique hairstyle which resembles a drill, which he took a few years prior to the start of the story, due to an incident involving a childhood love interest of his named Jaqueline. the story of his hairstyle was that Jaqueline got involved in a murder case as an accused, but was actually innocent. Grevil, knowing of his sister's genius at solving mysteries, went to her, begging her to help him. Victorique, having not experienced love herself, is confused as to what it is, and tells Grevil that he must change his hairstlyle to a drill if he wants the case solved. begrudgingly, he complied, and Jaqueline was aquitted.
His relation with his sister is a strained one, her having a, unusually cruel childhood, and him being unable to acknowldge her publicly, but personally respects her for her genius intellect.
He often uses Kazuya to look after and keep an eye on his sister, and develops a trust with him over time, even giving him the pet name and variations of "Squirrel".