Riko Mine, alias Riko Mine Lupin IV, attends Tokyo Butei High School as an A-rank student in the Inquesta department. Descended from the legendary thief Arsène Lupin yet lacking his supernatural talents, she resents references to "4th" or "Fourth," feeling they negate her individuality; she insists on being called simply "Riko." Born March 31, 1993, Riko's childhood shattered at age eight when her parents perished in a car crash. A man named Vlad, posing as a relative, imprisoned her in an underground dungeon. There, she survived on rotten rat meat and muddy water, clad only in rags. This captivity permanently stunted her growth to 147 cm (4'10") and forged her later passion for ornate Gothic Lolita fashion. Vlad aimed to force her to bear a "Lupin V" heir for Illuminati Uprising (IU) experiments, exploiting her bloodline. Riko cultivates a facade of playful stupidity: sleeping in class, using third-person speech, and earning renown as her cohort's "biggest idiot." This *burikko* persona includes assigning nicknames (e.g., "Ki-kun" for Kinji Tohyama) and overtly flirtatious behavior, especially toward Kinji, whom she sexually provokes to trigger his Hysteria Mode. Beneath this mask lurks "Dark Riko" — a ruthless, calculating alter ego emerging under stress. Dark Riko employs coarse language, emanates an intimidating glare, and radiates palpable bloodlust. Her fighting style transforms from elegant to vicious, mirroring her trauma and buried hostility. Embracing her heritage as "Lupin the 4th," Riko operated as IU's "Butei Killer," seeking to surpass her ancestor by defeating Sherlock Holmes' descendant, Aria H. Kanzaki. Her scheme involved manipulating Aria and Kinji into a Holmes-Watson partnership to kill them, proving superiority where Lupin failed against Holmes. She sports dual Walther P99 semi-automatic pistols—modern successors to Lupin III's Walther P38—plus two daggers for melee, earning the moniker "Quadra" for wielding all four weapons simultaneously. Her most prized possession is an Irokane cross enabling prehensile control of her long blonde hair. Vlad later steals this cross, spurring Kinji and Aria to recover it. Riko's expertise spans bomb specialization (deploying landmines and Claymores), information gathering via Butei High's underground networks, and masterful disguise including voice mimicry. Initially an antagonist, her betrayal of IU leads her to join Team Baskerville. Relationships within the team prove complex: she harbors lingering hostility toward rival and fellow Quadra Aria, evolving into reluctant camaraderie. She develops genuine romantic feelings for Kinji, seeing him as a potential lover, though her overt seduction clashes with Aria and Shirayuki Hotogi. Her deepest grudge targets Vlad, whose presence or mention risks triggering violent outbursts. Her arc transitions her from vengeful operative to Team Baskerville member, though early loyalty remains ambiguous. Collaborating with Kinji and Aria after Vlad steals her Irokane cross signals a shift toward alliance. Her backstory and motivations—overcoming familial legacy and trauma—add depth, blending antagonism with redemption.