The Seven Deadly Sins aid the Sky People against a powerful group of demons hellbent on resurrecting a demonic beast sealed over 3,000 years ago.

Ousai Academy was originally an all-girls high school. Due to the declining birth rates in recent years, it was converted into a co-ed school. The first year male students would find themselves surrounded by girls and unfortunately, Tsuda Takatoshi is one of them. What's worse, he gets scolded on his first day by the student council president Shino Amakusa, which did not give a good first impression of him. Tsuda also meets the other student council members while getting scolded, and in the end, he gets late for class. As an apology for ruining his morning, Shino lets him join the student council for various of "reasons" and he accepts it, or rather, he's forced to accept. Thus begins his days as Tsuda soon realizes that he's the only normal student in Ousai Academy...

The second part of a two-part movie. The story takes place one year after the TV series.

Ichiban Ushiro no Dai Ma?, also known as Demon King Daimao, is a Japanese light novel series written by Shotaro Mizuki and illustrated by Souichi It?, published by Hobby Japan under their HJ Bunko imprint. The first volume was published on February 1, 2008, with a total of 11 volumes available as of December 2010. A manga adaptation began monthly serialization in the September 2008 issue of Akita Shoten's magazine Champion Red, and a 12-episode anime adaptation by Artland aired between April and June 2010 on Tokyo MX and other channels.