Kumiko is a youthful-looking woman with bobbed hair.
Kumiko has a stubborn, controlling, and parsimonious personality. She manages her husband's finances strictly and investigates his activities to an extreme when his schedule deviates from normal. Despite not working herself, she is overly conscious about money, carrying a brand-name handbag and asking Banba and Lin to keep their investigation as cheap as possible.
Kumiko's stubbornness is apparent in her persistent belief that her husband is cheating on her. When Tadafumi disappears, she is more spiteful toward the woman he may have run away with than anxious about his well-being. Even though she has strong doubts regarding Tadafumi's faithfulness, she does maintain some open-mindedness and will not accept any truth without definite evidence.
Kumiko and Tadafumi were married when Kumiko was 29, and she has supported her husband as a housewife throughout their marriage. Recently, she had become suspicious of her husband's late hours and searched his belongings in their room while he was away from home. She found the business cards of several Club Eve hostesses in his desk drawer and the names and numbers of several women in his cell phone contacts. When she visited the club, she witnessed and photographed her husband leaving in his car with two women.
Niwaka Samurai Impersonator ArcEdit
Kumiko visits the Banba Detective Office and immediately regrets her decision after walking in on Banba half-naked and fighting with Lin and seeing the state of disorder inside the office. As she presents her case and evidence, she rebukes Lin's sarcastic commentary. Banba accepts her case, and they agree on a two-week investigation period.
Several days later, Kumiko visits Banba's office to inform Lin that her husband has not come home for several days. Rather than appearing anxious over his disappearance, she has decided that he has eloped with one of the hostesses. Even when Lin reveals to her that Tadafumi has been working at Club Eve, Kumiko is set on believing that he is cheating regardless, but Lin has already concluded the investigation and settled upon Tadafumi's innocence. Kumiko requests that Lin search for her husband and agrees to a small additional fee. He begrudgingly accepts the task and passes it along to Enokida.
Due to her certainty in her husband's infidelity and her resentment toward the other woman, Kumiko decides to have the woman killed. She visits Undergroundjobs.com and hires the cheapest assassin she can find, a killer calling themselves the Niwaka Samurai. She meets with Yamamoto and Abe, disguised as the famous killer and his manager, and gives them a 100,000 yen advance payment for the job. Due to their suspicious appearances, she follows them and takes photographs of the pair and their van. They disappear with the money, and several hours later, Kumiko realizes she has been swindled. She visits the office again, to Lin's annoyance, and requests that he retrieve the money. Lin is slightly impressed with her sleuthing skills and passes the task along to Yamato.