Kasygano Haruka and his twin sister, Sora, have lost both their parents in an accident. Having no money, they decide to move out of the city and into a rural town where they once spent summers with their late grandfather. At first everything seems familiar and peaceful, but things begin to change as Haruka remembers events from his childhood.
Anime [12 Episodes]
There's quite a few romance anime shows that are based off of adult games. Most of the time the anime itself has no mature themes in it and most people are shocked to find out where the story originated from. This is one of those shows that started off as an adult visual novel. Unlike the others, it does keep a lot of the mature scenes.
Visual novels are usually set up in a choose your own adventure type format. Most games have multiple girls that you can get with, and each of them have their own endings. Yosuga no Sora stays true to it's origins in this aspect. The entire series is broken up into mini-stories. Each story follows the path of a different girl and even has an ending for each one. I've never seen any other anime do this before.
If any of you did the math, you'll know that there are not enough episodes to cover all the possibly females. So, what the creators did is they added a mini-episode after each episode that covers the remaining female. I haven't seen this done very often and for it to carry across the entire series as a exasperated story is pretty impressive.