My Stepmom's Daughter Is My Ex

is a Japanese romantic comedy light novel series written by Kyōsuke Kamishiro and illustrated by Takayaki. The series began serialization on the online novel website Kakuyomu in August 2017, with a print version beginning publication under Kadokawa Shoten's Kadokawa Sneaker Bunko imprint in December 2018. The light novel is licensed digitally in North America by J-Novel Club. A manga adaptation by Rei Kusakabe began serialization online by Fujimi Shobo via Niconico Seiga website as part of the Dra Dra Sharp and Dra Dra Flat brands in April 2019. An anime television series adaptation produced by Project No.9 aired from July to September 2022. Synopsis When they were middle schoolers, Mizuto and Yume were a completely normal couple. Between flirtations and shouting matches for minor reasons, the two students stayed together until they entered high school, where they finally decided to break up. What they do not know is that fate sometimes has many surprises in store, and that they will be reunited again as stepbrother and sister only after two weeks. Indeed, their respective parents are about to remarry and the former couple will have to live under the same roof on a daily basis. In order not to hinder their parents' happiness, they accept the situation and decide to put in place the rule of brothers and sisters, according to which the first who feels attraction towards the other loses. Characters Mizuto is Yume's ex-boyfriend who became her stepbrother when his father, Mineaki, remarried her mother, Yuni. He shares a fondness for reading with Yume and has high grades, leading to a competitive relationship with her. He and Yume were born on the same day. His mother died when he was young.