After having nightmares concerning the events surrounding his older brother's death, Kinji ends up following Aria who goes to the police station to talk with her mother, Kanae, who is currently incarcerated as a suspect of the Butei killings. She mentions that Aria needs to find a partner to use her ability, as well as someone known as 'E.U.' The next day, Kinji hears word that Aria will be flying back to London. Later, Kinji goes to meet Riko, who reveals information concerning the Butei Killer, which also mentions his brother who died during a 'sea-jacking', before pulling some moves which sends Kinji into his Hysteria Mode. With his heightened senses, Kinji deduces that Aria's plane is being targeted by the Butei Killer, managing to get on it before it takes off. During the flight, Kinji learns that Aria has a fear of lightning before the Butei Killer announces his hijacking. They soon discover the culprit is Riko herself, who reveals herself to be the great granddaughter of Arsene Lupin, who organised the bike and bus jackings to target Aria, the great granddaughter of Sherlock Holmes, so she can surpass her great grandfather. She also reveals herself to be the one who killed Kinji's brother, who was also her lover. Riko and Aria enter an intense duel, but Riko gains the upper hand by using the true nature of the Quadra, which allows her to manipulate her hair, managing to shoot Aria in a critical area.