|Hataraku Maou-sama! Light Novel Volume 0|
|Release Date||September 10, 2014|
|Number of Pages||344|
|Cover Character/s||Sadao Maou, Shirō Ashiya, Hanzō Urushihara|
|Next Novel||Light Novel Volume 0-II|
Hataraku Maou-sama! Light Novel Volume 0 (はたらく魔王さま！0) is the 1st special edition book of Hataraku Maou-sama! Light Novel series.
Volume 0 contains several stories. The first story tells about how Satan Jacob (Sadao) unified the Demon World. There is also a short story on an incident where Emilia has to deal with a lizard infestation and also a story which takes place in Japan, the winter before the incidents in Volume 1.
The Demon King and Co at work! -a long time ago-
Chiho asks Ashiya to tell the story of how Sadao came to become the Dark Lord. Ashiya begins by telling her how Satan Jacob (Sadao) was being trained by Camio, who was a powerful clan leader but whose clan was dying out slowly. Besides being weak, they were also getting attacked by Lucifer, who was a rogue demon who attacked all the clans in the area at the time. Satan Jacob decides to challenge Lucifer and successfully gets him to join his alliance.
Next, he heads to the Ashen Horn Clan territory with his new alliance to challenge Adramalech, the powerful clan leader for the Ashen Horn Clan. After sneaking into the city with Lucifer and Camio, Satan Jacob challenges Adramalech to a battle on the condition that if he wins, he will absorb the Ashen Horn Clan into his alliance. Despite Adramalech not taking him seriously at first, Adramalech is surprised by Satan Jacob's ferocious fighting and is defeated. At the same time, Camio's troops capture the city and the Ashen Horn Clan is absorbed into the alliance.
Twenty years later, Satan Jacob and his new Demon King Army is set to unify the entire Demon World. He has conquered many other smaller clans at this point but is set on conquering the Iron Scorpion Clan, a powerful clan led by Alciel (Ashiya). The first time they had fought, the Demon King Army was beaten badly. So Satan Jacob has been training the troops for a long time in order to prepare them for a rematch. He then challenges Alciel to a battle, to which Alciel, unsure about this new upstart, accepts. He first has his troops skirmish with Alciel's troops to see how Alciel's troops fight. He captures two of Alciel's troops and using a charm offensive, convinces the two troops to divulge the strategies used by Alciel's army. The next time they meet, the Demon King Army overwhelms the Iron Scorpion clan and Satan Jacob ends up challenging Alciel to a one on one battle. Faced with no choice, Alciel fights him.
At this point, Chiho has to get ready to go home, so Ashiya tells her that he lost the battle and eventually the Demon King Army unified the entire Demon World. When Chiho leaves, Ashiya reminiscences about what he didn't tell Chiho. After he lost the battle, he was expecting to be killed, but Satan Jacob tells him that he was going to absorb his clan into the Demon King Army and then to conquer the Melabranche army, the most powerful clan in the Demon World, then the capital city. It takes time, but eventually the entire Demon World is conquered, which leads to the events of the invasion of Ente Isla 200 years later.
The Hero and Co at work! -a long time ago-
Emilia, Olba, Emerada, and Albertio are in the Southern Continent nation of Tharlaj, helping to fight off an invasion of Malacoda's Melebranche army. The Tharlaj emperor has not heard back from Wathewlama, an important city which could unify the nations of the Southern Continent into a powerful nation called Harlun. He asks they go investigate what has happened.
Before they leave, Olba finds out from a messenger that Crestia Bell is in Wathewlama. They make the long journey over the desert and speculate about the idea of dragons, which had been seen in the Southern Continent coming from the Malebranche army. When they get to Wathewlama, they are told by the leader that there has been a massive infestation of lizards attacking the city and is threatening to overwhelm the city and asks for Emilia's help. Emilia reluctantly agrees.
Olba meets with Crestia Bell, and learns from her that the lizards can be cooked and eaten. He gets an idea and proposes to the leaders and the group to cook and eat the lizards in order to scare off the rest of the lizards from attacking the city. Although Emilia and Emerada are horrified by this suggestion, the plan is set in motion for a huge city wide festival to be held to cook and eat the lizards they can catch. Eventually the lizards stop attacking the city and the traveling group leaves. On the way back, they notice a dead Melebranche squad who was trampled to death by the lizards and Emilia comments even their enemies can't get any reprieve from the lizards.
The Demon King, Hero and the High School Girl! -a happy new year-
Set on Christmas Day just months before the incidents of Volume One, Sadao and Ashiya are working as part time workers trying to sell cakes. They are taking on the extra work during Winter Break to make some more money despite Sadao already working at MgRonald’s. Inadvertently, they manage to sell a cake to Emi, but they do not recognize each other.
The next day, Rika and Emi discuss their plans for the break at work, and on the way home the train Emi is riding has to make an emergency stop. Two high school girls try to offer their seat to an elderly woman, but the woman refuses. However, Emi manages to convince the woman to take a seat and even offers to accompany her to her final destination, which is coincidentally Emi’s destination. The two girls thank Emi, and later it is revealed to be Chiho and her friend Kaori.
On New Year's Day, Chiho and Kaori decide to head to a shrine, however the shrine is packed with people. Chiho accidentally bumps into a man and in the confusion she ends up getting more money than intended, and then gets her fortunes. The man, who is Sadao, is disappointed that he lost his money and ends up getting a bad fortune initially, but decides to try his luck again. At the same time, Emi is also there and gets her fortune, and it turns out all three of their fortunes are good. This is the last time they meet before their worlds collide that spring.