Natsumi Yukihira is the main character of the Japanese Detective series Unfair and of the movie and two of the specials.
Natsumi is a female Detective in the Japanese Police whose father was killed prior to her joining the force and it had a profound impact on her outlook. After joining the Japanese Police she eventually became a detective, she had one of the best arrest records on the force with her unorthodox methods always getting results though she did get flak from her superiors and some of her colleagues (most notably a by the book detective named Yuuji Kokubo)
At some point in life she married a reporter named Sato Kazuo and had a daughter Mio.
One day Natsumi was forced to shoot a 17 year old suspect who died thus her reputation suffered in the face of double standards, it put such a strain on her marriage that she and Kazuo divorced both share custody of Mio and they maintain a friendly if at times strained relationship.
At the start of the series Natsumi intervenes in a hostage situation where the negotiator was just making a robbery suspect holding a woman hostage even more agitated she intervened by taunting the man, daring him to kill the woman and even suggesting how to do it. This cause the woman to faint but it made the suspect easier to handle and Natsumi took him into custody.
While it was successful it wasn't all that well received and her superior Tetsuo Yamaji does upbraid her (though he wasn't as bad as some other people including Kokubo) but he assigns her as a partner a young rookie detective named Kazuyuki Ando and within the first episode, she goes on the trail of a serial killer.
Natsumi is a very unorthodox detective who genuinely cares that the victims get justice. To Natsumi taking the bad guys down is all that counts and the results are what's important. Natsumi almost sees the world in Black and White.
Also Natsumi is shown to be good at reading people as to how she realize how the suspect in the hostage situation would not have killed the situation and seemed to understand the negotiator was making things worse.
Natsumi while she is committed to her job she is a caring mother to her daughter Mio though often her work pulls her away and remains friendly with her ex-husband though at times it seems their relationship can be strained at times.
Natsumi also has no modesty as is shown when she sleeps naked and a few other scenes in the series.