Betrothed to My Sister's Ex (ずたぼろ令嬢は姉の元婚約者に溺愛される, Zutaboro Reijō wa Ane no Moto Konyakusha ni Dekiai Sareru; lit. "Loved by Her Sister's Former Fiancé") 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 ten 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 ten tankōbon volumes. An anime television series adaptation produced by LandQ Studios aired from July to September 2025.
Contents
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 Kyros, 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 Kyros sends his marriage proposal. Anastasia goes missing and is presumed dead when heading to Kyros's home; resulting in Marie being sent to comfort him. Kyros realizes his mistake with the sisters names, but Marie cannot understand it herself; resulting in a very long struggle to break her out of her mindset.
Characters
Marie Shaderan (マリー, Marī)
Voiced by: Rena Motomura
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.
Kyros Granado (キュロス グラナド, Kyurosu Gurando)
Voiced by: Daiki Hamano
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 son; 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.
Anastasia Shaderan (アナスタジア, Anasutajia)
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. Ten volumes (including eight volumes published digital-only) have been released as of May 2026.
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 eleven tankōbon volumes as of July 2026. 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 aired from July 5 to September 20, 2025, on the Animeism programming block on MBS, TBS, CBC and BS-TBS. The opening theme song is "Gesshoku" (月蝕; Lunar Eclipse), performed by Krage, while the ending theme song is "Marie" (マリー, Marī), performed by Myuk. Crunchyroll is streaming the series. Tropics Entertainment licensed the series in Southeast Asia for streaming on the Tropics Anime Asia YouTube channel.