First of all, lets make things clear. THERE ARE SEX SCENES WITHIN THIS SERIES!! and this component usually makes people want to simply watch this series as a hentai. If you are planning on doing so, you will be trading a GREAT anime with a HORRIBLE hentai because those scenes are short and not very exciting. Instead, the sex scenes create an unique mood for the story development.
Story 9/10 Yosuga no sora was originally a PC visual novel, this means that the story cannot possibly lack content. The story is very unique, instead of having a million girls liking the main character at the same time, the story focuses on one heroine for a few episodes then goes back to a "save point" and starts a new story with the next one.
I have to split the art part into two.
General art (how the characters look) 8/10
Mood art (what makes the current situation or story more interesting)10/10 The art of this anime is capable of completely expressing the character's feelings. The artist is not simply making the characters blush and changing the eyes and eyebrows to express a character's emotions. Instead, the artist uses the body language of the characters. ( the way a character is standing, sitting, lying down, getting f**ked)
Sound 9/10 The voice acting for most characters is very satisfying.
The background music and sounds were generally good. ( with a few scenes that have great background music and sounds) The opening is one of my favorite anime openings. The op song beautifully expresses the general feeling of this anime.
Character 10/10 In general (because I might flood the review with my own opinions and lower the quality since i have too much to say）The character portrayal is great, partially thanks to the art; each character has a very unique and attractive personality which also makes the individuality of the characters extremely strong.
Enjoyment 9/10 The only thing holding me back from giving this series a 10/10 for enjoyment is the intense conflicts made one episode seem very long and made me want to take a break. Which is also the reason this anime is enjoyable.
I would suggest this series to everyone, especially people who likes interesting conflicts and romance.
PS: The visual novel is still much better so why not give the VN a chance while you're at it. Both the art and music are amazing and the stories are more developed in the VN :D