I don't like my big brother at all!!

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?

Akiko is thrilled to be reuniting with Akito, the handsome older brother she hasn’t seen in years! In fact, she might be a little too excited. This pint-sized cutie has a big brother complex, and she’s not interested in sharing his attention. Unfortunately for little sister, she and Akito won’t be living alone: three gorgeous girls from the student council will be along for the ride!

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?!

When Konoe Moyako and her little brother, Akira, were young, he said he wanted to marry her. Naturally, Moyako decided that her little brother was a complete pervert who was obsessed with her. Now that they're both teenagers, Moyako is convinced she needs to "rehabilitate" him. However, it seems that the "perversion" is entirely in her imagination, and she can't seem to help turning completely innocent situations into creepy ones in her mind!