Mizuto and Yume used to date each other at least until they broke up once they entered high school. In a twist of fate, the two exes end up becoming stepsiblings due to their parents marrying each other. As they set up their terms, they decide to have a competition of seeing which sibling would become attracted.
My Stepmom's Daughter is My Ex (Mamahaha no Tsurego ga Motokano datta) is a light novel series written by Kyosuke Kamishiro and illustrated by Takayaki, which began publication in 2017. The novels are licensed in English by J-Novel Club. It received an anime adaptation under Project No. 9. that began airing in July 2022 during the summer season.
The manga provides examples of:
- Agony of the Feet: Yume has a bad memory of when she wore a traditional yukata to a summer festival and likens the geta to a torture device.
- Big Brother Instinct: Mizuto claims this trope applies in regard to the guys at school ogling over Yume, but he obviously has... other reasons to want to keep them away from her.
- Bland-Name Product: Episode 5 briefly shows several fictitious soda brands, including Caco-Cola, Tanfa, and Munite Miad.
- Boob-Based Gag: Higashira's G-cup breasts are often the butt of many jokes.
- Childhood Friend Romance: Kawanami and Akatsuki grew up together and previously dated, but have broken up by the time of the main story. However, when Mizuto brings up this trope they furiously deny it.
- Clingy Jealous Girl: Despite her no longer being Mizuto's girlfriend, Yume can't help but feel envious of any girl that gets close to Mizuto, especially Higashira.
- Deadpan Snarker: Mizuto is often snarky at his stepsister's expense.
- Flirty Stepsiblings: The whole plot centers around this trope; while Mizuto and Yume previously dated before, they broke up, only to find two weeks later that their respective parents have decided to marry each other and they'll now all live under one roof. The rest of the series is about them trying to live as stepsiblings but still dealing with their lingering feelings for each other.
- Ms. Fanservice:
- There is a lot of focus on Higashira's breasts. Aside from that, in the anime there are several lingering shots of her feet given her habit of slipping her shoes and socks off when reading.
- Yume herself has her moments. She tries to tease Mizuto with her Modesty Towel only for it to fall off. She has the second largest bust after Higashira, and she also has her foot scenes.
- Not a Date: In Episode 4, Kawanami arranges for Yume and Mizuto to go on a "date" to the aquarium in an (unsuccessful) attempt to persuade Akatsuki that they only have eyes for each other. Yume tries to convince herself to that it's perfectly acceptable for siblings to go on outings together, but she's repeatedly reminded of her and Mizuto's real first date in middle school.
- Pseudo-Romantic Friendship: A one-sided version occurs with Yume's friend Akatsuki, who's obsessed with the idea of marrying Mizuto— not because she actually likes him all that much, but because she desperately wishes to be Yume's "little sister". Her fantasies about married life with Mizuto involve living with Yume and even sharing a room with her.
- Retroactive Stepsibling Relationship: Exactly What It Says on the Tin. Mizuto and Yume used to date, then broke up, and then their parents married each other.
- Shipper on Deck: Kawanami describes himself as a passive spectator in love and is more interesting in helping Mizuto and Yume get together when he realizes there's something between them.
- Shout-Out: In episode 8 of the anime, Isana is seen reading the first volume of Haruhi Suzumiya.
