Contract 1
Chapter 1 Cover
Title How to Conquer Your Step-Sister
Kanji 妹ができた日
Rōmaji Imouto ga dekita hi
Chapter 2

How to Conquer Your Step-Sister is the 1st chapter of Shinmai Maou no Keiyakusha series.


Basara is now living with her two step-sisters in a new town and a new house, because his father Jin is planning to remarry. However, he doesn't know that his step-sisters, Mio and Maria, are hiding a strange secret. The two reveal their true identity when Basara's father leaves the house on a business trip - they're demons. Could this be the start of a very drastic turn on Basara's life?


Mio Wakes Up Basara

Mio wakes up Basara

In a dream, a young boy is confronted by a man wielding a sword. The boy stands in front of a little girl, vowing that he'll protect his sister until the end.

A young man wakes up from the dream, saying that it pains his chest, no matter how many time he sees that dream. As he opens his eyes, Basara wakes up to find Mio sitting on top of him. Mio prompts Basara to get up and lifts up his blanket, revealing erotic books hidden underneath. Mio is infuriated, and hits Basara with one of the books, making the two fall from the bed. Basara lands on top of Mio, who punches him on the stomach and calls him a pervert.

Downstairs, Basara opens the fridge and grabs some milk, but as he turns around he is greeted by a little girl named Maria, wearing what appears to be an apron and nothing else. Basara spits out the milk because of Maria's outfit and asks why she is naked. However, Maria turns around and shows that she is wearing clothes underneath. Basara's father Jin greets him, but Basara yells at him not to leave stuff on his bed, much to his father's confusion. Maria says that the books are her doing, saying that she gave them the books as reference for training his sisters, but Basara tells her that he doesn't need them. Mio comes downstairs, and complains that Basara is hitting on Maria. Basara, Mio and Jin seats themselves while Maria serves food. Basara tells himself that since the two girls arrived, things haven't been peaceful.

Basara and Mio's First Encounter

Basara and Mio's not so good first encounter

A week ago, Basara and his father were in a restaurant, discussing his plans of getting married again and preparing to meet the other family. His father reminds him that he wanted a little sister and that he should be glad, and wonders if they will arrive at the meeting place soon. Basara stands up, saying that he'll wash his face. As he pushes open the bathroom door, he sees Mio inside with her underwear down. As Basara turns to leave, he realises Mio is about to scream, so covers her mouth and defends himself, saying it was an accident. After he moves his hand, she slaps him, sending him flying. Mio, obviously upset, starts kicking him; but Basara's father asks them what they're doing before Mio lands her kick, startling the two.

It was then revealed that the two were guided on the wrong table, then Basara's father apologizes for the act that Basara has committed. Mio and Maria introduces their selves, then Jin tells them that they'd be counting on the two and comments that Basara seems to have a liking for Mio, and the latter adds that it appears to be true, since he even entered the toilet while Mio is still in it. Basara begins to defend himself again, but Mio asks if he's making excuses again, but forgives him after Basara apologizes. Basara then inquires about the two girl's mother, Chihaya, but his father tells him that she wont be coming, then Basara, excuses their selves along with his father.

Not far away from their seat, Basara questions the reason why their mother cannot come, and Jin explains to him that it's because Chihaya had to go overseas for work, and wanted Jin to look after the two girls, since he and Chihaya would be worried for the two girls to leave alone. Basara wonders if the two were to live in the same house as they live, but his father tells him that he'll be renting a new place, and that way, they'll see if they can get along as a family. The two men then returns on their seat, Basara states that he agrees on living with them together, and knowing them as well. The two then thanks Basara, but Mio follows it up by saying that if Basara peeks on her again, she will kill him. Then on the front of their new house, the four stood in front of it, while having their picture taken, saying that the picture would be sent to the girls' mother who's on overseas.

Basara and Mio Flees

Basara and Mio flees from the thugs

Basara, along with Mio on a ride, says that he'll show her around, and would grocery while they're on it. Mio then inquires about the dream Basara had earlier morning, but Basara answers that it is about something that happened to him while he's still leaving on the countryside, resulting on a trauma, then tells to himself that there's no way he can discuss a dream like that to a normal person like Mio.

At the supermarket, after the two finishes what they need to buy, Basara tells Mio that he'll get the bike and instructs Mio to go to the exit with the cart. At the exit, as Basara spaces out, Mio's earlier question pops out along with other images, leaving him shocked. He then snaps out of it, then says to himself that he still can't get used to that dream no matter how many times he has seen it, and comments on how things would get better if ever he could forget it. Then from a distance, Mio is surrounded by three guys, asking her to hang out with them for a bit. Basara arrives at the scene, saying that Mio is with him. Mio mentions Basara's name, but one of the guys makes fun of his name then the two laughed, then proceeds on saying that his name is nerdy, making Basara pissed. He then hits the guy who made fun of his name with this bike, shocking Mio. As the two were about to do something to Basara, a container with a pepper were thrown at them, causing them to sneeze, while the two makes their escape.

Basara Sent Flying

Basara sent flying by Maria

Somewhere, after Basara ensures their safety, Mio apologizes on what happened, but Basara tells her that it's not her fault. Seeing that Mio is wearing a saddened expression, he tells her that they'll be having a detour. They ended up on a place where the whole town, as well as the sunset can be seen, whist Mio admires the view. Mio then inquires on how he know such place, on which Basara answers that when they came to inspect the house, he heard that there's a famous park somewhere and thought of coming next evening. He then proceeds on saying that he'll save Mio how many times, since it's natural for a family to help each other, like how she woke up Basara ealier morning. Mio then comments that Basara seems like a big brother now, but just a little. Basara then invites Mio to go back since Maria is waiting, then Mio agrees. The woman then glances back at the view, then wears a saddened expression again.

That night, Jin says that he'll leave, because of a job from an old customer. He then states that when the father is away, it's the eldest son's job to protect the family, then hands out Basara the first photo they had, and says that he'll leave things to him. On the window, Maria is seen peeking, and tells Mio that they should begin. As Basara goes back inside, he sees Mio and Maria having serious expressions, and Maria asks if Jin has left, on which Basara affirms. Mio then speaks up, saying that he wants Basara to leave the house. Just as he is about to ask what Mio means, Maria raises her hand, and a blast hits Basara, which sends him flying. Maria approaches him, and surprised that Basara is calm, saying that the people who see "Magic" for the first time falls into panic.
Maria Explains Everything

Maria reveals everything to Basara

She then begins transforming while saying that Magic is real, and proceeds by saying that other than humans, other races exists, such as demons. Basara, obviously shocked, asks Mio on what's happening, but Maria interrupts her speech, by saying that he's being impolite to the future Demon Lord. Maria continues on saying that the ones who oppose them demons, called heroes also exists, and proceeds by saying that what doesn't exist is is the talk about being remarried, and reveals that she is a Succubus that can manipulate dreams, and implanted a memory on Jin to obtain information for Mio. She states that Basara is the next one, asking him if she would leave him memories living in an unfamiliar relative's house with two girls. Basara then questions Mio if what Maria is saying is true, and if she's been lying to him and to Jin since they meet. Mio just simply responds that they would be taking the house and says goodbye to him, saying that it is enjoyable. Maria then tells a now saddened Basara that he will forget everything the next moment, then a large flash of light illuminates through the window. The tranquility is now then shattered.

Characters in order of appearance

  1. Basara Toujou
  2. Mio Naruse
  3. Maria Naruse
  4. Jin Toujou

Abilities, Items and Magic Used


  • None


  • None


  • Transformation
  • Memory Implant
  • Pressure Blast

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