Boku wa Imouto ni Koi wo Suru is I'm in Love with my Little Sister in english and from the title we can already see where this OVA is heading. The story doesn't incorporate many different elements to fully flesh out the story however considering the length of the OVA it is very much understandable.
Story: The story was not your most original however actually incorporating the genre of incestuous relationships is for me a first for anime. The story is basically as you know it, forbidden love that cannot flourish for obvious reasons and the emotional conflict that comes as a result. There isn't much story either rather it conveys the emotional struggle that the siblings experience during their daily lives. The story at first seems to drag along and then suddenly jump start into a really fast pace and then slow down to a slow jogging pace.
Art: The first impression of the art reminds me of a typical shoujo manga as the character's hair seem silky and long, the art of the environment is what really caught my attention as everything seemed rather life like (except the school grounds) but the art was pretty good other than that there really isn't much that makes the art appealing.
Sound: Well the sound wasn't very noticeable only does the OP and ED really stand out, the OP is just instrumentals that convey a relaxed, tranquil mood while the ED is some random rock group that personally I thought had very bad taste in making music.
Character: The characters weren't out of the ordinary rather Iku is just a cheerful young girl while Yori is a frustrated teen that can't seem to calm his emotions. There wasn't really much space for character development as their love interests were already set from the beginning. Basically what character development consisted of was resolving inner conflict and realization of personal feelings.
Overall: Overall the OVA wasn't the best out there but it wasn't the worst, it really brings out the theme that romance isn't always perfect out there, love cannot overcome all obstacles but we can always try our best to maintain it.