| Sora Kasugano|
|First Appearance||(Anime) Episode 1|
|Portrayed By|| |
The main female protagonist .
She is a quiet, fragile and reclusive girl, fraternal twin sister to the protagonist. Yet beneath Sora's angelic doll like appearance lies a troublesome personality that’s prone to withdrawn laziness and a rather severe lack of social graces. In episode 10, she becomes more considerate and caring towards Haruka after she decided to not trouble Haru too much and tries her best to take care of him. She seems to be very lonely when Haruka isn't with her. Also she is very jealous when she sees Haru with another girl. In the manga she tends to be more helpful and caring towards Haruka, like cooking when he can't and she doesn't seem to spend to much time on internet. But, besides Haruka she seems to act friendly towards Akira too.
Sora has gray eyes and silver hair. She has a perfect, doll-like appearance and is often seen as a fragile and weak girl. Whenever she goes to school (or some other places) she uses a twintail hairstyle. She usually unties her hair at home. She is 152 cm tall and is often seen carrying a rabbit doll, which she received as a present from her mother before she and Haruka left the village and which lends her a deceptively child-like character. She wears black ribbons, but when she was younger, she used to wear white ones.
The traumatic loss of their parents, her deep bond with Haruka and a kiss she shared with him as children causes her to fantasize about him. While she shields the extent of her feelings for him in public, she experiments with herself while fantasizing about being with him. She hates Nao because of her relationship with Haruka and the fact that Nao raped Haru when they were young. Although she hates Nao, it was implied that they were once good friends.
At the end of her route, she wins Haru's affection by confessing her love to him and making love to him as he was caring for her when she had a fever. After they get caught making love by Nao and Kozue, he attempts to break off the relationship and she attempts suicide by drowning. Haruka tries to stop her but his inability to swim only causes the both of them to sink. Sora changes her mind upon hearing him whisper "save me" and she drags Haru to shore. Afterwards, they decide to travel to a far away country, promising their friends to come back with souvenirs.
- Mr. Kasugano (father) (deceased)
- Mrs. Kasugano (mother) (deceased)
- Haruka Kasugano (elder twin brother/ husband)
- Grandparents (mentioned)
- Kasugano distant family relatives (mentioned in episode 12)
- Nao Yorihime (They were friends in the past but Sora caught Nao having sex with Haru, which is the reason why she hates her.)
- Ryouhei Nakazato
- Akira Amatsume
- Kazuha Migiwa
- Motoka Nogisaka
- Kozue Kuranaga
- Like Motoka, she seems to have a high libido. This is proven by the fact that after the first time she had sex with Haruka, she was eager to do it "many times again".
- She has an irrational fear of mosquitoes as displayed by her attempt to kill one with hair spray.
- She is portrayed as heavily dependent on Haruka in the beginning.
- She is almost never seen without her stuffed rabbit doll that her mother gave her when she was hospitalized. (Anime)
- She is the only character who has attempted suicide.
- She goes to great lengths to seduce Haruka or at least to get his attention.
- She spends most of her time surfing the internet. Haruka describes it by saying "She can't live without it".
- She enjoys consuming chips and other various snacks as well as instant foods.
- She seems to like Pocky as shown in the opening scene in both the Anime and the Visual Novel, where she enjoys a box with Haruka
- She is the only anti-social character of Yosuga no Sora.
- She is the only character to get married and become pregnant.
- While having different names, the VA for both the anime and the game are the same, Haruka Shiranami is a pseudonym for Hiroko Taguchi