My Stepmom's Daughter is My Ex

When his father remarries, Yuta Asamura winds up sharing a roof with his new stepsister, Saki Ayase, the hottest girl in his grade. Carrying the scars of their parents’ troubled divorces, they vow to maintain a respectful distance. But what starts as cautious camaraderie blossoms into something deeper from shared experiences. Is it admiration, familial love, or something more?

Is insanity hereditary? Shougo Mikadono's beginning to think so, because the terms of his late father's will seem crazy and following them may drive Shougo bonkers as well. Oh, it sounds simple at first: before Shougo can claim his VERY large inheritance, he just has to start attending a certain new school and find a nice girl to marry. It's a little unromantic, but perfectly do-able, right? After all, all the girls seem quite friendly, so all Shougo has to do is find one he has something in common with. EXCEPT, and here's the kicker, it turns out that Shougo has WAY too much in common with one of them, because she's actually his long lost sister! And he has no idea which one she is! Will Shougo meet and court his Miss Right without committing something very morally wrong? Can he find his future bride without slipping into the wrong set of genes? And if his little sister does reveal herself, just how much will be revealed and under what circumstances?

For high schooler Akiteru Ooboshi, the whole youthful experience thing—like fun, friendships, and even having a girlfriend—is a complete waste of time. So when his best friend’s sister, Iroha Kohinata, keeps teasing him, Akiteru naturally finds it annoying. She practically lives in his room, she’s always on his bed, she’s just a raging storm of clinginess! Why is she only annoying around him?!

Kazuki has been awaiting 10 years for the day when her neighbours moved back to their old house. She has a crush on Yuuji, whom she considers as her first love but to whom she never managed to express her feelings for him before they moved out. Yuuji often comes over to play with Kazuki, Kazuki's older sister Hatsune and Yuuji's sister Marie when they were kids. Her ideal depiction of Yuuji was soon shattered when he turned out more than she had expected, him acting all ecchi during their reunion. With their parents off in South America, both families must learn to live with each other and rekindle the childhood feelings they shared together. Things get even more crazy as they attend the same school.