Kinshiro Toyama (Hiroshi Tamaki) is the new chief at Kitamachi police station. He is enthusiastic to solve cases which interests him. He bickers over pretty much everything with veteran detective Yozo Minami (Masahiro Takashima). Minori Aikawa (Miori Takimoto) is a rookie detective who wants to become a veteran detective.
Rieko Nishiwaki (Miki Mizuno) is released from prison after spending 8 years incarcerated on a false charge. She seeks out her former best friend who betrayed her and she comes across a young murderess.
Rena Sasaki (Keiko Kitagawa) is a beautiful woman with excellent memory and intelligence. She becomes a private detective and risks her life to chase down evil private detectives, because her younger sister was murdered by a stalker. The person that provided information to the stalker on her sister's location was a private detective.
Shinobu Satomi (Tori Matsuzaka) works in the Mobile Investigation Unit of The Tokyo Metropolitan Police Department. The Mobile Investigation Unit conducts the initial investigation at all crime scenes. He works with Yuki Inokuma (Fumino Kimura). They are a couple, but they keep their relationship a secret at work. They both hope to work at the #1 Investigation Station. One day, they meet beautiful Kara Tachibana at the site where a dead body was found. Kara Tachibana appears at the other crime scenes involving grotesque murders. She shows an interest in Yuki Inokuma. Shinobu Satomi thinks it's a bad sign for Yuki Inouma. To protect his girlfriend from danger, he struggles to find uncover the truth behind the serial murder cases and Kara Tachibana’s identity.
Ikuo and Tatsuya are orphans. They live at Mahoroba’s house which is a child and family services home. At their elementary school, they see Teacher Yuko, who took good care of them like a real older sister, killed right in front of them. Ikuo and Tatsuya tell the police what they saw, but the case is covered by a police officer wearing a gold watch.
15 years later, Ikuo (Toma Ikuta) now works as a detective. He is a good person and his arrest rate is the highest at the police station. Meanwhile, using his handsome appearance and cleverness, Tatsuya (Shun Oguri) becomes a high ranking yakuza.
Detective Ikuo and Yakuza Tatsuya have a singular purpose, which is to find the man wearing the gold watch, dig out the truth and reveal the dark side of the police organization.
Nagisa Kinomiya (Maki Horikita) is a detective for the 7 Investigation Division. The team consists of female detectives and they seek out female criminals and to help female victims. Nagisa Kinomiya has a special ability to hear the mind's of others. To shutout other people's emotions, she wears a headset, but, when working on a case, she uses her special ability. At crime scenes, Nagisa Kinomiya can hear the left behind voices of criminals and victims.
Ryo Saeba (Takaya Kamikawa) is a private detective and a sweeper who rids society of evil. He is also known as City Hunter. He works with partner Kaori Makimura. An accident leads to Kaori Makimura's death and her heart is transplanted to Xiang-Ying. Xiang-Ying then appears in front of Ryo Saeba.
Akagi Shigeru is a young, white-haired mahjong genius. One summer in 1965, he ends up facing off against Washizu Iwao, Japan’s King of Darkness who has amassed enormous fortune and power, at the request of his acquaintance, the rogue detective Yasuoka. As the observer, Ogi Takeshi, a leader of the henchmen of Inada-gumi watches over them, mahjong with special rules called Washizu Mahjong begins. It is a life or death struggle with Akagi’s fresh blood and Washizu’s entire fortune at stake.