Through the Baidu search engine in China, the first promotional image for the anime was leaked Mamahaha no Tsurego ga Motokano Datta (My Stepsister is My Ex-Girlfriend). In addition to this, some stills from the first promotional preview were revealed and it is also mentioned that the project is scheduled to be released this year.
A certain boy and a certain girl, both in high school, became a couple, flirting with each other, arguing over trivial things, frequently feeling irritated with each other, ended up breaking up at their graduation. And the two of them, Mizuto Irido and Yume Ayai, ended up meeting again in the most unexpected way. It turns out that his parents, both divorced, met, fell in love and got married, now making them step-siblings. The ex-partner, aware of their parents’ feelings, establishes a “sibling rule”, in which the one who becomes aware of the other loses. But, having so much contact living together, can they really ignore each other?