The Devil Is a Part-Timer is a novel series that has been written by Satoshi Waghara and the illustration has been done by Akio Hiiragi. The novel series saw its publishing in February 2011 for the first times and it needs to be said that the 1st season has 11 volumes.
Satan Jacob is a demon king and the entire storyline is centered on him since he is Satan himself. This demon king has only one task and that it to be the ultimate ruler and conqueror of Ente Isla and four continents that this fantasy world has. He is not alone in this, he has several generals who help him to accomplish this mission, and they are Alciel, Lucifer, Adramelech, and Malacoda.
However, they surely have the opposition to their intended conquest of Ente Isla and it is a very brave hero called Amelia Justina. She is also not alone in her struggle to save her world, and she has a lot of helpers and companions. We should also point out that she even succeeded to kill Adramelech and Malacoda. Faced with the evident defeat, Satan decided to leave to Earth with Aciel, and they found themselves in Tokyo. They did not go to Earth in their true forms, but they actually took the forms of humans in order to blend in. On Earth, they do not have their magic powers and they survive by doing regular human jobs.
Amelia also followed them to Earth in the hope of finding them and destroying them. When she finally finds them, she is also in a human form as Emi Yusa. However, she does not have her powers on Earth as well.
Here, on Earth, both of them start to question who they are and their inner personalities. Both of them seem to come to the same conclusion that it is much easier to live as a human. They also tend to work on themselves and their qualities as persons.
It should be also added that they are not the only ones, numerous characters enter Earth from Ente Isla. It should be also mentioned that the demon king has some form of epiphany when he realizes that his intention to conquer Ente Isla should not have been the most important thing in his existence. He is the one who starts being fond of his human nature.
It should be also noted that the second season brings the change of the demon who starts to use all of his powers so that he could help people.
We do not have any information whatsoever regarding the release of Season 2. White Fox Studio is working on other anime projects, and this one would have to wait. We should also note that the discussion of even having the second season is still active, which has been confirmed by Satoshi Wagahara. So, this practically means that we do not know whether season 2 would even see the light of the day until we see the announcement from the studio regarding the release date.