A ghost of a girl Aisuke suddenly appears in the room of Yohei who was dumped by his lover. Aisuke, who has never experienced love during her lifetime, is very interested in "dating" and giving Yohei useless advice.
One summer day, 400 goldfish were found in the swimming pool of a secondary school. This is a story about the four 15-year-old girls who put them there.
The criminal library, dubbed the “Red Museum”, is a police facility that stores the investigation materials and evidence of major crimes where the statute of limitations has run out. Its director Saeko Hiiro is impassive and not good at communicating with people. One day, Satoshi Terada of the Tokyo Metropolitan Police Department’s First Investigative Division is assigned to be Saeko’s subordinate. Although he is bewildered by Saeko’s dispassionate demeanor, Terada starts to organize the data which is the primary responsibility of the museum. He encounters a traffic accident on the way to collect evidence. A truck has hit someone. When Terada rushes over, the victim utters the mysterious words “25 years ago... murder swap” and breathes his last. Once Saeko hears this, she declares a reinvestigation.
Karen is an ordinary high school student in Tokyo, but she sometimes recalls pieces of her childhood memories that she did not know before. During the process of getting her passport for a school trip, Karen views her family register. She learns that she had an older sister Yukari, who died at the age of 4. Karen also learns that her parents are not her biological parents and that she was adopted. Karen now wants to learn about herself. She lies to her parents and tells them that she is leaving on the school trip. Instead, she travels to Fukuoka where she was born. Her classmate Satoi Hogari accompanies her.
Detective Ukyo Sugishita confronts crime on the basis of his own convictions. He has a partner that works for him in the Special Task Unit. For the first 7 seasons, Ukyo’s first partner is Kaoru Kameyama. He is a good-natured, hot-tempered, straightforward and somewhat scattered detective. Beginning in Season 8, Takeru Kanbe replaces Kameyama. Contrary to his predecessor, Takeru is a lanky, cool, conceited and confident detective. From Season 11 to Season 13, Ukyo’s partner is a young detective Toru Kai. Toru is a son of Deputy Director-General of The National Police Agency. But he became a detective by his own effort. And starting with Season 14, Ukyo’s current partner is Wataru Kaburagi, an elite bureaucrat who came to the Metropolitan Police Department on temporary assignment. As the first partner without any career of a police officer, he will face challenging cases together with Ukyo.
Takashi Mikami, a University of Tokyo graduate, joins the Ministry of Education to reform Japan's education but is disillusioned by its reality. Transferred to a private high school, he takes a stand against the authorities, using his role as a teacher to push for change.
