Demon Lord Sister Arc
Shinmai Vol1 0008
Location Toujou Household
Hijirigasaka Academy
Media Duration
Light Novel Volumes
Light Novel List
Manga Chapters/Volumes
Manga List
Anime Episodes
Anime List
1, 2, 3, 4
Light Novel Chronology
N/A ←Demon Lord Sister Arc→ Hero Clan Arc
Manga Chronology
N/A ←Demon Lord Sister Arc→ Hero Clan Arc
Anime Chronology
N/A ←Demon Lord Sister Arc→ Hero Clan Arc

Demon Lord Sister Arc is the first and an introductory story arc of the Shinmai Maou no Keiyakusha series. This arc contains at least two story as one. The first story is about Basara's first meeting with his would-be step-sisters Mio and Maria under Jin's introduction, in which the later quickly creating the bond between both Basara and Mio via the "Master-Slave" ceremony. The second and last story involving Basara's and Mio's initial rivalry against Yuki and Yahiro (as Lars) after learning that Mio herself is a target of elimination by the Demon Realm's current faction and the Hero Clan members.


Basara and His New Little Sisters

In one dinner during a Summer Vacation, Jin asks Basara if he wishes to have a sister but Basara replies that he didn't remembered in making such request. As his father continues to tease him, Basara becomes infuriated as he views little sisters as "cheeky and crude", prompts Jin to believe that he is fine to have a younger sibling. When Basara asks his father regarding the questions however, Jin instead asks his son if he is glad to see his would-be sibling sooner.

The following day, both Basara and Jin are waiting at the family restaurant to meet their new family.
Vol1 17

An unexpected encounter.

Having mistaken the couple of mother and daughter as his new family members, who Jin apologizes to on his son's behalf, Basara rushes for the washroom to wash his face while accidently stumble upon Mio, who just finishes using a toilet while wearing her panties and watches him in a dumbfounded look. As Mio try to scream however, Basara hastily closes the bathroom door while covering her mouth and apologizing for the misunderstanding, seemly calming her down. After releasing from Basara's grasp however, Mio slaps Basara and scolds him for his previous action.[1][2] Just as she is about to punish him however, Jin enters the bath room to check the commotion that opts Basara and Mio responds to Jin simultaneously, much to their shock. Regardless, Jin reintroduces Mio and Maria to Basara and because their "mother" is working overseas, the step-sisters will be staying at Toujou Household until her return to discuss their remarriage, which means that Basara had to get along with the Naruse Sisters despite their early differences-especially Mio who is still fuming over the restaurant bathroom incident.[3]

Ways to Conquer Little Stepsisters

Daily Life As a Family

Step-sisters Secrets?!

On the next night, Jin is leaving the house by taxi while telling Basara to take care of the house. During their dinner however, Mio "requests" Basara to leave the house whilst Maria using her magic to trap Basara. As the boy is perplexed over the sudden situation, Maria reveals themselves as Demons to Basara while Mio deems Basara as unworthy.

Basara and Maria Conflict

Basara deflects Maria's magic.

To both girls surprise however, Basara resists and dodges Maria's magic while summoning Brynhildr and revelas hismelf as a Hero despite his former relationship with Heors and Demon. The battle quickly ends and it begin where he defeats the Naruse sisters effortlessly but spares their life as Basara tells them to leave since the family does not take deception kindly, even if it is from the Demon. Just as both girls eventually leave house, Basara receives a phone-call from his father who reveals Wilbert's demise and the Hero Clan declaration to terminate Mio as they ranked her as the S-Ranked surveillance subject, simply because other demons also tried to kill her in order to harvest Wilbert's will. After scolding his father for not telling the truth earlier but entrusted by Jin to protect Mio and Maria, since he is heading to the Demon Realm, Basara rushes towards outside the house to find the girls.

Vowing to Protect

Elsewhere, Mio laments over the incident and despite Maria cheers Mio by telling her that they could go for another place to stay, she instead refuses as she states that deception is never her style and continue to find a place to stay, which Maria reluctantly complies.

Threshold's Trust and Unexpected Reunion

(To be added...)

Until your Sadness becomes Nil

(To be added...)

What he wants to Protect

After nursed by Yuki for five days since the park incident, Basara returns to school and heads to the school's rooftop where he coincidentally encounters Yahiro. As Yahiro claims that he is "glad" to see him recuperated, Basara isn't easily fooled as he summons his blade and points it at Yahiro, who becomes silent but reassured by Basara that he isn't going to hurt him. Both students discuss their next move as Basara negotiating an uneasy truce with Yahiro as he holds the fact of reporting Yahiro's failure to his superiors as leverage and as act of trust from Yahiro's intention of not killing him and Maria, in which Yahiro reluctantly agrees in Basara's terms. As Basara asks Yahiro regarding Mio's foster parents's killer, Yahiro briefly reveals the killer to be Zolgear.

Part 2

(To be added...)

Part 3

Meanwhile in the Demon Realm's forest, Jin receives a phone-call from an unknown recipient regarding Basara's latest battle, though he is somewhat relief that he belief in his son before finishes his call. In his search for a woman and witnesses the Demon Realm's change under a new ruler's reign, which also involving Mio as well, Jin remarks to Basara that the struggle is the only beginning as he will face an inevitable fate that involves Mio and his unknown past, which only Jin knows too well.

Light Novel, Manga and Anime Differences



Major Battles

  1. Basara vs. Mio and Maria
  2. Basara and Mio vs Yuki
  3. Yuki vs Lars
  4. Basara and Mio vs Lars[4]
  • Characters in bold represents the winner of the battle/duel.

Story Impact

  • This introductory arc introduces most of the important characters, specifically Basara, Mio, Maria, Yuki and Yahiro/Lars.
  • Under the protection of both Basara and Jin (who later revealed in traveling to the Demon Realm), Mio and Maria are officially become new members of the Toujou Household.


(To be added...)


  1. Manga Chapter 1
  2. Anime Episode 1
  3. Anime Season 1 Episode 1
  4. Anime Episode 3