Following the death of their parents in a tragic car accident, Haruka Kasugano and his twin sister Sora are left orphaned. Rather than live with relatives, Haruka seeks comfort in fond memories of the past and decides to move to the rural house left to them by their grandparents, who are also deceased. Sora, unwilling to be separated from her brother, decides to follow him. Although Haruka is glad to relive memories of the summer vacations he spent at the countryside, Sora is much less enthusiastic.Haruka reconnects with his childhood friends Nao Yorihime, the neighborhood older sister, and Akira Amatsume, a miko. He also befriends his new classmates Kazuha Migiwa, daughter of a local politician, and Ryouhei Nakazato, who is in Haruka's class because he ended up getting held back a year. Haruka also meets Motoka Nogisaka, a maid in the employ of Kazuha's father.Yosuga no Sora ("Sky of Connections") is a visual novel developed by Sphere in 2008, with illustrations by Takashi Hashimoto. The novel averts the standard Unwanted Harem by having Haruka express interest in a heroine early on in the game. The story then branches off and shows his developing relationship with the chosen girl. Each route is a story of drama, summer love and coming-of-age as Haruka adapts to his new responsibilities as Sora's de facto caretaker and learns how to provide the heroine with emotional support.The visual novel also has a 2-volume 2010 manga adaptation illustrated by Takashi Mikaze, primarily concentrating on the Sora angle, and published for Comp Ace, as well as a 2010 anime adaptation for the Fall 2010 lineup directed by Takeo Takahashi using a similar episodic format akin to Amagami SS: each heroine has an arc dedicated to her, but rather than an Alternate Continuity to reset an entirely new arc, the next set of episodes features a "What If?" for Haruka in vying for another heroine's heart.A sequel/expansion fan disk called Haruka na Sora contains bonus material, extended scenes and includes scenarios for Kozue Kuranaga, Class Representative of the twins' homeroom, and Yahiro Ifukube, Akira's Parental Substitute and Motoka's best friend.
Big Damn Heroes: Nao pulls this off in Episode 9 (Nao 4) when she jumps into a burning bus stop to rescue Sora's rabbit doll, kicking down a large board locking her in after a few seconds of suspense. Not bad, considering that Sora hates her after she caught her presumably raping Haruka many years ago.
Bittersweet Ending: At the end of the Sora arc, the Kasugano twins move overseas, hoping to find a place where their incestuous relationship will be accepted. Whether they actually find happiness is left ambiguous. Meanwhile, Kozue is left an emotional wreck when she realizes that Haruka won't return her feelings, more so when she caught the twins in the act.
Black Comedy Rape: Matoka does this to Haruka in the omake of Episode 7 (Nao/Sora 2) while drunk. Not that Haruka minds it...
Bleached Underpants: Played straight in the manga, even in such crucial scenes as Nao's "rape" flashback and Nao and Kozue catching the Kasuganos in the act. Averted in the anime, where while not extremely explicit, Motoka is shown masturbating (and implicitly on a frequent basis) and the show has no qualms showing nipples in full detail. Then Episode 4 (Kazuha 4) literally gives the starting act of a sex scene, and Episode 6 (Akira 4) goes all out showing Akira in all sorts of surprising sex positions.
Break the Cutie: Kozue's entire Sora Arc experience. Averted in the manga, where she somehow starts to get better, accepting the twins' relationship and wishing them a safe return after the group of friends the twins made receive a mail through Kazuha from Haruka, promising to return to them one day.
Broken Bird: On one hand, Sora could probably use a slap or two for her selfish, needy behavior. On the other hand, she's such a psychological mess that it's hard not to feel sorry for her.
Clingy Jealous Girl: Sora, full stop. It isn't particularly helped by catching Nao apparently "raping" Haruka.
Coitus Uninterruptus: In Episode 9 (Nao 4), When Sora walks in on Nao and Haruka having sex, the latter's reaction is to keep thrusting, though there is a possibility he didn't notice Sora until a few moments later, as he was understandably caught up in the act.
Conspicuous CG: In the anime, most car scenes are blatant ones, as well as train scene, but especially the fans, where it seems the animators spent a lot of time in the initial scene showing the fan on the train.
Double Standard: Rape, Female on Male: Deconstructed by a past incident where Sora caught Nao apparently "raping" Haruka. Nao genuinely regrets doing it and thought Haruka hated her for it. Turns out Haruka was okay with this — he was just surprised from it since it was his first time — and he wanted both of them to get over it. It helps that the anime is a lot less clear on whether or not the incident was consensual, and Sora is very biased on the matter.
Erotic Dream: Late in Sora's arc, Haru dozes off in class and dreams that his sister has snuck under his desk to give him a blowjob.
Festival Episode: The summer festival is a common event in the game and anime, usually around the end of an arc.
First Kiss: Haruka and Kazuha in Episode 3 (Kazuha 3), initiated by the former. While it seems Kazuha would resist, she actually gives in and implied her feelings to him in response. Likewise, Akira willingly gives this and more in the Furo Scene of Episode 5 (Akira 3).
Follow the Leader: Played with — while it seems like it follows the story-telling plot from Amagami SS, where after one arc is over the series retcons the entire thing to give way for the next one, the anime adaptation for this visual novel has branching episodes, each fork representing different choices.
Hotter and Sexier: Compared to most post-midnight anime. Whereas most networks still shy themselves from showing uncensored nipples after midnight, Yosuga no Sora dares to go the whole nine yards and show full sex scenes on network TV, akin to HBO's Rome and The Sopranos.
Idiosyncratic Episode Naming: Every episode works in the name of a character or two while keeping the title an actual sentence. A prime example is Episode 4 (Kazuha 4) — while translated as "Haruka's Heart", in katakana it's spelled "harukazuhaato", containing both the names of Haruka and Kazuha, the Episode's main players, in the title.
Idiot Ball: Why didn't Haruka's grandmother confirm with Kazuha's parents whether the babies were switched instead of telling Akira in her diary?
Ill Girl: Sora, but it never really comes up, except in the manga. One early scene in the anime has Sora spend time at the hospital when she was younger. Haruka also briefly mentions this during Sora's arc.
Why the already clingy Sora has a special hate for Nao — she walked in on them having sex several years prior. And in episode 8 (Nao 3), it happens again.
Taken Up to Eleven In, well, Episode 11 (Sora 4), in which Nao and Kozue walk in on Haruka taking his sister from behind in the entryway of their house. At the exact moment Sora gets an orgasm.
I Want My Beloved to Be Happy: There are elements of this in Nao's acceptance of Haruka's relationship with Sora in the latter's arc. Reinforced by the fact that she tries to remain composed even as Kozue was having a mental breakdown.
Little Sister Heroine: Sora — possessive and prone to thinking of him during "special" times, and an actual blood sister.
Mood Whiplash: The omakes at the end of each episode is... out of place with the episode preceding it. It gets even more ridiculous when the chibi-like figures shape-shift, such as Motoka's snakish figure in episode 3. Or Akira's head being large. Coincidentally, these are also seen in the second ED.
My God, What Have I Done?: Nao thinks she might have raped Haruka, carrying the guilt of it for years before things clear up.
Near-Rape Experience: Haru nearly rapes Nao in Sora's arc at a Love Hotel due to his frustration over his sexual attraction for Sora. He stops, however, after hearing Nao crying and screaming for him to stop.
No Export for You: The visual novel. The fact that the Fan Translation was taken down by the developers and Sphere's website is blocked for all foreigners doesn't help, too.
This applies to the anime, too. It was only licensed in Taiwan at the time of writing this and there's no interest in license the anime in the US.
Non-Identical Twins: Subverted — Kazuha and Akira share the same birthday and father, just not the mother.
Parental Abandonment: Akira was abandoned by her father into Yahiro's care, much to the ire of her sister Kazuha — at least not openly, because it would hurt Kazuha's mother more than he already has. Then it turns out that Kazuha's mother raised Akira all along in lieu of her since-deceased biological mother. She has also given Akira a pendant as a reminder of maternal love, only to start neglecting her because of the implications of Akira being her husband's bastard daughter, though they eventually reconcile at the end of the latter's arc.
Porn with Plot: Being an eroge on one hand, and an anime based upon an eroge on the other, it's kind of to be expected for it to contain porn. It also has surprisingly in-depth plot lines and doesn't portray the relationship between Haruka and Sora as some Excuse Plot for fetishistic wish-fulfillment but shows both how much it torments Haruka that he's having a deviant relationship with his sister as well as the issues that have played a part in shaping Sora's inability to make the same reflections.
Squick: In-Universe, Haruka was revolted and ultimately driven to tears at the sight of Sora masturbating while moaning out his name in Episode 10 (Sora 3).
This can also be summed up as Kozue's reaction upon discovering Haruka and Sora's relationship.
Stepford Smiler: Akira's cheerful mask fades when she's alone, when she's reminded of her mother, or when she sees Yahiro. The latter has her coming close to breaking down. In a way, her personality mirrors that of "Sayori-hime", the local goddess whose shrine she works in.
The Unfavorite: Kazuha is certain that Akira this. She turns out to be wrong.
Unresolved Sexual Tension: Initially between Haruka and Kazuha, though very quickly resolved. An even faster resolution occurs between Haruka and Akira. It took only half an episode for Haruka to remember her and for Akira to jump him in the bath.
Untrusting Community: Notably averted — the members of the community in general were greatly indebted to the Kasuganos' grandparents and are more than willing to help them out. In the Sora arc, the main reason the Kasuganos decide to leave was due to the taboo nature of their relationship (and the fact that Nao and Kozue caught them having sex).