As someone who is not a huge fan of sex in media – I found Aki-Sora to be a difficult read.
I found myself cringing or feeling bored in some parts.
Why did I read it then? To prove to a friend that I actually could.
Warning: There is a lot of sex and other mature themes in Aki-Sora.

Story: 6/10
Aki-Sora is about a young boy who has a sexual relationship with his sister.
The story is about a young boy's sexual exploits until about 20 chapters in. The redeeming parts of the story that make Aki-Sora a worthwhile read – are the character backstories. I found the backstories of Aki, Sora and Nami's parents to be quite intriguing as well as the building of the relationship between Kana and Nami.
Other than that the story is mostly disconjointed sex scenes at the end of each chapter (which served as a buildup to the 'climatic' sex scene). This is where Aki-Sora suffered for me.

Art: 4/10
Yes the characters are cute; but I sometimes found it hard to interpret which character was saying what in each panel.
The illustrations of various body fluids also made me a bit queasy.

Characters: 7/10
Aki-Sora is a character driven manga in which we get to see the different character's inner turmoils.
In some cases – this is brilliantly executed; when not over shadowed by the constant sex.

Enjoyment: 3/10
I found myself forcing myself to read through some parts. I prefer action stories with a lot going on as well as brilliant characters. Aki-Sora is not a story like that.

Overall: 5/10
Aki-Sora only gets an average from me. It's not because of the incest – that doesn't bother me.
I know that it is an ecchi manga – which isn't my type of story.
It isn't a masterpiece; but I do recommend it to people who enjoy ecchi/incest type of stories.