Betrothed To My Sister's Ex

is a Japanese light novel series written by Tobirano and illustrated by Mai Murasaki. It began serialization online in October 2019 on the user-generated novel publishing website Shōsetsuka ni Narō. It was later acquired by Futabasha, who have published eight volumes since April 2020 under their M Novels f imprint. A manga adaptation with art by Chikage Nakakura has been serialized online via Futabasha's ''Gaugau Monster'' website since July 2020 and has been collected in nine ''tankōbon'' volumes. An anime television series adaptation produced by LandQ Studios premiered in July 2025.

Premise

Marie was abused and taken advantage of her entire life by her parents, resulting in her lack of self-esteem. On her birthday, her parents present her sister Anastasia as the star of the evening; leading her to stay in the garden to avoid attention. This leads to her meeting duke Cyrus, who falls in love with Marie due to her sweet personality. However, because of the misunderstanding caused by her parents, Marie's name gets mixed up with her sister's when Cyrus sends his marriage proposal. Anastasia goes missing and is presumed dead when heading to Cyrus's home; resulting in Marie being sent to comfort him. Cyrus realizes his mistake with the sisters names, but Maria cannot understand it herself; resulting in a very long struggle to break her out of her mindset.

Characters

;
:
:The heroine, who lived a very Cinderella life. Having spent her life being called ugly and stupid, Marie is frustratingly unable to understand that Anastasia was ''never'' whom Kyros wished to marry; even when he states to her face that he got their names wrong because of her poor wording. She is meek around others and tries to conform to what she thinks is appropriate, which only makes things worse for her; everyone at Kyros's estate cannot figure out what she likes in order to help her adjust better. However, as she spends more time free of her parents' abuse, Marie begins to discover how much she enjoys being free to choose.
:In truth, she has been running her family's estate due to her father being too much of an imbecile. All the abuse she suffered was to keep Marie from ever desiring to leave after seeing just how bad a shape her home was in.
;
:
:The duke whom fell in love with Marie. He was born to his father's foreign mistress Liu-Liu, while the official duchess never bore a child; with the untimely demise of his father, along with Kyros's own accomplishments on the battlefield, he became the next duke without any backlash. He's loathed noble women who only ever wanted to marry him for status, which is why he was so drawn to Marie; she didn't care about status and had a caring heart. Even though he repeatedly explains to Marie that he got their names mixed up, Kyros is left utterly frustrated with her being unable to accept that she is NOT a replacement for her sister. This comedically leads to him showering her in unnecessary gifts and learning Marie has no clue as to how to choose what she likes on her own.
:Kyros ultimately decides to bring the abuse Marie has suffered to the public eye, believing it will also help save her homeland from her father's incompetence.
;
:
:Marie's younger sister. She was close to Marie as a child, but her parents forced them apart in order begin conditioning Marie into being their slave; while pampering Anastasia to make her ignore what was going on. Anastasia noticed the horrible things, but because she took Marie's face value word that she was fine, she tried to ignore it for years. Once the engagement to Kyros arrived, Anastasia could tell from the dress sent as a gift that he had gotten her and Marie's names mixed up. She used the carriage ride to run away and hide out as a boy, getting a job as an apprentice tailor.
;
:
;
:
:Head maid of Kyros's household. She is polite and very no-nonsense, but looks after Marie with kindness; seeing she has such poor self-esteem that she has to constant direct her into not overreacting. Within the early days of her serving Marie, Mio fires two maids sent by to be the ladies-in-waiting; they had be exacerbating Marie's confidence issues in a long term plot to become Kyros's mistresses. This not only angered Mio, but made Kyros so upset her gave them a death glare. Mio often investigates or goes undercover to find information for Kyros, leading to her leaving the estate to learn more about Marie's background.
;
:
:Kyros's mother and the mistress of his late father. While she is fluent in both her native and the local language, she has trouble writing and reading the latter. Liu-Liu very much likes Marie and makes the effort along with Kyros and Mio to help her get past her unnecessary self-doubts. When Marie explained she did most of the talking and paperwork for her father, Liu-Liu realized that the entire reason that her parents didn't want her to go was because they couldn't do the work themselves.
:Liu-Liu can often be found in the library, where she bonds with Marie over their love of literature.
;
:
:The chef of Kyros' household. He is a large and very emotional man who tends to cry frequently and is easily moved by praise of his cooking. He tends to cook in excessive amounts, due to having a larger eating capacity.
;
:
;
:

Media

Light novel

Written by Tobirano, ''Betrothed to My Sister's Ex'' began serialization on the user-generated novel publishing website Shōsetsuka ni Narō on October 23, 2019. It was later acquired by Futabasha who began publishing the series with illustrations by Mai Murasaki under their M Novels f light novel imprint on April 15, 2020. Eight volumes (including six volumes published digital-only) have been released as of January 2025.

In April 2025, Seven Seas Entertainment announced that they had licensed the series for English publication beginning in January 2026.

Manga

A manga adaptation illustrated by Chikage Nakakura began serialization on Futabasha's ''Gaugau Monster'' website on July 24, 2020. The manga's chapters have been collected into nine ''tankōbon'' volumes as of June 2025. The manga adaptation is published digitally in English on Comico's Pocket Comics website. In April 2025, Seven Seas Entertainment announced that they had also licensed the manga adaptation for English publication beginning in January 2026.

Anime

An anime television series adaptation was announced on July 29, 2024. It is produced by LandQ Studios and directed by Takayuki Kitagawa, with series composition and episode screenplays handled by Kenta Ihara, characters designed by Akiko Satō, and music composed by Kujira Yumemi. The series premiered on July 5, 2025, on the Animeism programming block on MBS, TBS, CBC and BS-TBS. The opening theme song is , performed by , while the ending theme song is , performed by . Crunchyroll is streaming the series.

Episodes

See also

* ''Akuyaku Reijō no Naka no Hito'', another light novel series by the same illustrator
* '' I'm the Villainess, So I'm Taming the Final Boss'', another light novel series by the same illustrator

Notes

References

External links

* at Shōsetsuka ni Narō
*
*
*

{{Animeism

2020 Japanese novels
2025 anime television series debuts
Anime and manga based on light novels
Animeism
Crunchyroll anime
Futabasha manga
Japanese romance novels
Japanese webcomics
Josei manga
Light novels
Light novels first published online
Romance anime and manga
Seven Seas Entertainment titles
Shōsetsuka ni Narō
Webcomics in print