Introductory Arc[]
Riko first makes her first appearance by doting on Kinji with his seemingly sexual relationship with the new transfer student however she is quickly silenced once Aria begins shooting up the room. She would later be hired by Kinji in order to investigate Aria's background and, following a payment of dating sims, Riko delivered an extensive profile on Aria, detailing her career back to her time as a fresh recruit at the English branch in London.
Butei Killer Arc[]
Riko would primarily be operating behind the scenes for the early parts of the arc, however her unbeknownst influence was very heavily felt by Kinji and Aria. Using her ties to IU, she smuggled Jeanne d'Arc and Kyouchikytou into academy grounds and began setting the stage to draw Aria out. Using an arcade voucher, she attempted to manipulate Kinji and Aria to bond and form a partnership. It seemed everything was going as planned as they were the first Butei on the scene to respond to a bus jacking she staged, however the duo fell out shortly after the case so Riko had to take a more direct approach.
By feeding Kinji information that the butei killer may be hijacking the plane Aria is taking back to England, Riko finally set up the perfect scenario for Lupin and Holmes to clash once again. Riko rode her moped to the airport and snuck aboard the plane as a flight attendant, taking control of the plane before Kinji could arrive. Riko managed to get Kinji and Aria to make up and, now that the two are partners again, made an announcement in the "voice" of the butei killer that the plane has been hijacked. Kinji and Aria immediately make their way to the plane's bar and confront Riko. After revealing herself as the descendant of Arsene Lupin, a vicious fight between Aria and Riko that resulted in Riko's near capture. However Riko caught both of them offguard by revealing her ace - hair manipulation from her Irokane rosario, resulting in Kinji being disarmed and Aria being critically injured.
Riko would ultimately allow them to flee as her "Dark Riko" personality caused her sadistic bloodlust to lapse her better judgement but she slowly followed, constantly taunting them as she made her way down the plane. She would eventually catch up and corner them in Aria's private room and, following a brief exchange with Kinji, seemingly saw through the trap they had set by unloading her gun into the closet behind her rather than the bump on the bed. Her "Dark Riko" personality once again had seemingly clouded her judgement as Aria was niether on the bed nor closet but in the overhead compartment. Caught completely off guard, Aria managed to cut off Riko's twintails and she and Kinji held Riko under arrest. Not one to come quietly, Riko used her Irokane powers and rocked the plane causing the butei to lose their footing as Riko fled.
Kinji would confront her alone and, after failing to convince him to join IU in order to be reunited with Kana, Riko blew open a hole in the plane's cabin and jumped out of it, using her special clothes as a parachute to safely fly off into the night. Presumably the IU itself was following her as not too long after returning to IU, she would be dismissed for her failure and her rosario, and thus her Irokane abilities was taken from her.
Heist Arc[]
Riko would return in her trademark flamboyant fashion by tricking Kinji into thinking Aria was calling him to her room. After successfully putting him into Hysteria mode, Aria would intervene on the two and chased Riko to the roof where the two seemed to be on the verge of finishing their previous fight. Fortunately, Hysteria Kinji settled the conflict (particularly by flustering Aria) and Riko recruited the duo for a heist on Vlad's mansion in exchange for being a witness for Aria in her mother's trial.