The Testament of Sister New Devil

新妹魔王の契約者 (Shinmai Maou no Testament)

6.7(392,340)

MAL Score

Ranked #6825

Popularity #321

Action
Ecchi
Supernatural
Harem

Episodes: 12
Duration: 23 min per ep
Aired: Jan 8, 2015 to Mar 26, 2015
Status: Finished Airing

Synopsis

Basara Tōjō’s first day with his new family goes off the rails fast—starting with an awkward run-in in the bathroom and ending with his father introducing two girls as his new stepsisters: the confident redhead Mio Naruse and the petite, silver-haired Maria. What looks like an abrupt change in household dynamics turns into something far more dangerous when the sisters reveal their true identities.

Mio is the former Demon Lord’s only daughter, and Maria is her succubus attendant, forcing Basara to confront his own past as a former member of the Heroes, long-standing enemies of demons. Despite that history, he chooses to stand between them and the threats closing in, sealing a master–servant pact with Mio to keep her protected. With watchful Heroes, hostile demons, and secrets Basara can’t easily leave behind, the uneasy new family must survive in a world where trust comes at a cost.

Otaku Consensus

The Testament of Sister New Devil earns its cult visibility by letting Hisashi Saitou’s brisk direction and Takao Yoshioka’s compact series composition fuse harem escalation with surprisingly credible sword-and-magic combat. Fans consistently point to the character art, punchy action beats, humor, and emotionally effective music as the parts that work; the dominant criticism is that the ecchi material is so frequent and prolonged that it dilutes villain writing, dramatic tension, and the fantasy mythology. Its reputation is less “failed fantasy” than “divisive fan-service vehicle with better fight staging than its detractors expect.”

Why You Should Watch

Watch this if you want the High School DxD itch scratched with fewer brakes: demonic power politics, succubus mischief, swordplay, magic, and an unapologetically horny harem engine packed into 12 episodes. It is best for viewers who prefer ecchi as the main attraction rather than a side garnish, but still want real action choreography, urban-fantasy stakes, and a male lead who is not written as a total passenger. The appeal is in the collision of tones: bathroom-comedy nerve, transformation-heavy supernatural fights, and contract-based intimacy scenes that push the TV version into censorship territory. If your patience runs thin when fan service stalls the scene, this will test you; if you like erotic harem fantasy with actual combat texture, it delivers exactly that lane.

Key Characters

M
Maria Naruse(VA: Kaori Fukuhara)
Maria is the series’ clearest signal that the succubus angle is not decorative, driving much of the show’s mischievous ecchi momentum and comic provocation.
M
Mio Naruse(VA: Ayaka Asai)
Mio anchors the harem fantasy with a mix of vulnerability, status, and explosive supernatural baggage that makes her more than a simple red-haired love interest.
Y
Yuki Nonaka(VA: Sarah Emi Bridcutt)
Yuki brings the Hero-side tension into the character dynamic, giving the cast a cooler, more martial counterweight to the demon-girl energy.
B
Basara Toujou(VA: Yuuichi Nakamura)
Basara stands out among ecchi-harem leads because fans often read him as unusually proactive, physically capable, and central to the action rather than merely surrounded by it.

What Makes It Stand Out

1
Production IMS produced the 12-episode Winter 2015 run, giving the season a compressed structure that moves quickly from domestic comedy into factional supernatural conflict instead of stretching its setup across a longer cour.
2
AniList’s tag profile is unusually blunt: Nudity at 92%, Female Harem at 91%, Demons at 87%, Succubus at 80%, and both Spearplay and Swordplay at 79%, accurately mapping the show’s mix of erotic charge and weapon-based fantasy action.
3
The TV broadcast became known for heavy censorship, which shaped reception as much as the content itself; discussions of the series often separate the censored viewing experience from the appeal of its more explicit presentation.
4
Critic and fan commentary repeatedly compares it to High School DxD, but the common verdict is that Sister New Devil has a more diluted story and thinner villains while still offering appealing character art and serviceable-to-strong action scenes.
5
The combat is not treated as incidental decoration: user reviews specifically single out believable fight scenes, a stable plot through the season, and a moving soundtrack as reasons the show retains defenders beyond pure fan service.

Fun Facts & Trivia

Fun fact 1: The anime adapts Tetsuto Uesu’s original story with original character designs by Nekosuke Ookuma, while Yoshihiro Watanabe handled the TV anime’s character design and Shinpei Kobayashi handled creature design.
Fun fact 2: Design work was split among Mami Imai, Mina Ootaka, Miyana Okita, and Takahiro Ishimoto, which helps explain the production’s emphasis on costumes, transformations, and demon-fantasy visual elements.
Fun fact 3: Its database footprint is strikingly lopsided: on MyAnimeList it sits at a 6.68 score and rank #6831, yet its popularity is #321 with 392,194 votes, showing how widely watched it is despite polarized ratings.
Fun fact 4: AniList tells the same story of divisive visibility, listing a 63/100 score alongside 2,373 favourites and tags that heavily foreground nudity, harem structure, demons, and urban fantasy.
Fun fact 5: User reactions in the supplied review sample range from 3/10 Not Recommended to 10/10 Recommended, with even a 9/10 review marked Mixed Feelings, making it a textbook case of an anime whose target audience and rejection audience are sharply separated.