Age: 16 years old
Height: 165 cm (5'5")
Weight: 54 kg
Weapons of choice: double Walther P99 for handguns, for backups a model 95 and double daggers for melee
Known as: "Quadra" and "Lupin IV"
Riko Mine Lupin the 4th (峰 理子 Mine Riko?) is a female student of Butei High school. She is a friend of Kinji's, whom she calls Ki-kun, and is enrolled with him in the Butei Inquesta department. She is ranked A (Second highest rank). Although known as the biggest idiot in Kinji's class, she seems to hold a lot of information including info on the students of Butei High school. She likes customizing her uniform into Lolita style and playing dating sim video games. (However, she looks too young to buy them so she asks Kinji to buy them for her.) Her weapons of choice are double Walther P99s for handguns and double daggers for melee. Like Aria, she has earned the title of "Quadra". Riko is apart of Team Baskerville(Aria and Kinchi are suspicious that she will betray them), who chose the affiliation Deen, yet the most of IU choose Grenada, and she was formerly part of that group. It is unkown on which side she will act on. She often gives others nicknames (Reki = Rekyu, Kinji = Ki-kun, etc. ). She also loves to flirt with Kinji alot through sexual manner.
Near the end of the first volume, Riko reveals that she is a descendant of Arsene Lupin. Although she is the descendant of Arsene Lupin, she was born with no special abilities. Her handguns are also a modern successor to Lupin III's signature weapon, the Walther P38.
Her real name is Riko Mine Lupin IV. Riko also reveals that she is the Butei Killer. She appeared to have an inferiority complex concerning the first Lupin and wanted to escape his shadow. Her plan was to make Aria and Kinji become partners so it could mirror the situation of Sherlock Holmes and Watson. Defeating both of them would mean she would become better than her ancestor Arsene Lupin who couldn't defeat Sherlock 100 years ago. She despises being called "4th" because she feels it removes her personal identity, as such she prefers "Riko".
Riko and Aria have similar traits: small stature, the title of "Quadra", twin-tail hairsyle (in Riko's case, her hair is not entirely split in half unlike Aria), and being the fourth generation of their families. She has a height of 147 cm (4'10") and weighs 54 kg.
It soon turns out that after Riko's parents died in a car crash at the age of 8, Vlad took her in by pretending to be her relative but then locked her up in his dungeon to attempt to create an ideal 5th Lupin descendant, since Riko had failed to inherit her predecessors' superior gene, and was therefore deemed a failure. She was mistreated horribly while imprisoned; she was provided with only rags to wear, and had to sustain herself only on dirty water and rotten meat. Unsurprisingly, this experience has left significant permanent effects on her; for example, her being forced to wear only ragged clothing may have contributed to her developing a love for fancy clothing, and it is said that the malnourishment is the reason for her currently petite stature.
