A mysterious creature destroys 70% of the moon. The creature then warns that if he is not destroyed by March of next year, Earth will be next. The creature also demands that he becomes the homeroom teacher for 3rd grade E class at Kunugigaoka Junior High School. The government is powerless to say no.
The creature then becomes the homeroom teacher of 3rd grade E class which consists of failed students including Nagisa Shiota (Ryosuke Yamada). The creature is called Teacher Koro.
Meanwhile, the government requests that the students try to kill Teacher Koro even though he possesses super powers. The government offers a 10 billion yen reward for whomever successfully kills him. The students are confused by the situation, but decide to kill Teacher Koro.
When their class begins with Teacher Koro, the students finds themselves having a good time with their new teacher.
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.
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.
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.
About 150,000 illegal entrants live in Tokyo. They are not recognised as refugees and live in poor conditions. To protect themselves, the illegals create a secret organisation. The organisation has a bank which Japanese Financial Services Agency is not involved with, a hospital that is not authorized by Japanese Ministry of Health, Labour, and Welfare and an illegals police force called "Dias Police." The only police officer in the organisation is Saki Kubozuka (Shota Matsuda). His age and nationality is unknown. Saki Kubozuka does not speak much, but he has a warm heart and strong sense of justice. He takes care of the weak and tries to maintain public order.
Balsa (Haruka Ayase) is a 30-year-old female bodyguard-for-hire. Her life changes when she saves Imperial Prince Chagumu who is being carried away by a raging river. They then attempt to return the great egg of the water spirit, which is in Prince Chagumu's possession to its source in the sea. Along the way, they are hunted by hired assassins.