In middle school, framed now in glorious golden light, Yume Irido used to be Yume Ayai, the timid girl with glasses who dated the clumsy and smiling Mizuto Irido. Born the same day, going to the same class, their love looked like destiny. But in time, he became this passive-aggressive teenage otaku with a genius complex, while she became a beautiful and manipulative social star, and they broke up. And then, without prior notice, Mr. Irido, a widower, married Mrs. Ayai, a widow. As the children had kept their parents in the dark about their relationship (talk about fearful symmetry), they are now quarreling and bickering in secret, while pretending that everything is A-OK in front of the happy couple. Things work out until they decide to make a bet to decide who will address the other as Onii-san or Onee-san: the one who “fails to behave in a sibling-like manner” towards the other, even in private, will lose. Make of that what you will.
While the premise makes me roll my eyes, I have enjoyed stories in which this kind of issue is treated with more seriousness, like From Up on Poppy Hill, or Love me, love me not. Having to adapt to someone who, having been romantically involved with you, is now off-limits, and having to learn to love them in a new way, could be the theme of a deep and hopeful story. My Stepmom’s Daughter is my Ex is not one of those stories, though. At first, I was hopeful when all these characters showed up initially and I saw the contrast between the past and present selves of Yume and Mizuto. But nope. It started with slightly sexually charged frames a few minutes in, and by the end, we were in “girl-in-a-towel-implausibly-falls-in-such-a-way-that-Shinji-I-mean-Mizuto-is-on-top-of-her” territory, only he’s all sexy and cool. This looks like it will be a much creepier Kazuya-sama, with lots of “as you know” dialogue thrown in for good measure. I think you’ll sleep much better if you just skip it.
Despite everything, know that My Stepmom’s Daughter is my Ex is streaming on Crunchyroll.