Haruka was a police officer from the small Rishiri Island near the coast of Hokkaido who was transferred to Tokyo and assigned as a partner to Detective Ito just the city entered a cycle of gruesome violence involving a Monkey. Haruka and Ito investigated numerous crime scenes and came to form different opinions on the vigilante, with Ito quietly supporting his actions while Haruka was determined to follow the law and bring him to justice.
While investigating the house of Akiko Yokohama, Ito was killed by Lady Bullseye, sacrificing his body to shield Haruka from a deadly projectile. After that, Haruka partnered with Akiko, who believed that one of the candidates for the new Prime Minister Itaru Ozu was behind the assassination of Ken Takahara. Together, they were able to uncover that the Bonsai Master, a major donor of Ozu's campaign, was involved. They convinced the Monkey to go after the Bonsai Master on the night of the election in which Akiko's uncle Shinji Yokohama had become the new Prime Minister.
However, the Monkey discovered that it Shinji and not Ozu was the one who ordered the assassination. The Monkey and Bryce involved Haruka and Yuki to enter the building in which the new Prime Minister was being protected. Haruka was wounded by Lady Bullseye but managed to kill her when Bryce briefly restrained the assassin. Finally coming face to face with Shinji, the Monkey was persuaded not to kill him by Bryce. However, when Haruka trined to arrest Shinji, he grabbed her pistol and tried to shoot her, so the Monkey had no choice but to kill him. Left with no other friends after having killed the Prime Minister, the Monkey was smuggled out of the country by Haruka, who put him on a place to USA while she herself left Tokyo to return home.