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?

Adventurer James Keziah Delaney returns to London from Africa in 1814 along with fourteen stolen diamonds to seek vengeance after the death of his father.

Oreimo follows the daily life of an ordinary high school boy named Kyousuke Kousaka. Kyousuke’s younger sister Kirino is a pretty fashion model, but also hides a dark secret of being an otaku of adult games. Kyousuke is the only person to whom Kirino reveals her hidden obsession and other issues.

The story begins with Keita Suminoe, a male third-year junior-high school student studying for his high school entrance exams. He is living in a home with his older twin stepsisters, Ako and Riko, who share no blood relation to him, and they help him prepare for his exams. Even though he initially dislikes himself for it, he begins to become attracted to his two step-sisters, and his two parents encourage him to eventually get married to one of them.