Nao Yorihime (依媛 奈緒 Yorihime Nao) is one of Yosuga no Sora heroines. She act like a big sister towards Haruka Kasugano, as a close and trusted childhood friend. Nao was sincerely devastated when it seemed she would never see the two siblings again.
Having a mature and diligent appearance, Nao is the most adult-like of the heroines with neck-length black hair that is has two white hair pins on the right side, dark blue eyes, a pair of round glasses and large breasts. She is considered a beautiful and attractive young girl.
Nao is a beautiful and intelligent who is an excellent swimmer, compassionate and maturity projects a sense of sisterly love towards others, though for Haruka Kasugano she has deeper, more intimate feelings towards him. When Haruka parted ways with her, she became apathetic, sorrowful and dreary around others, as she felt guilty about what she did to Haruka on that summer day.
Nao is Haruka Kasugano's next-door neighbor and childhood friend. When the Kasugano twins last visited the area, their departure was particularly painful for Nao, who had grown quite close to Haruka, to the point of raping him on one occasion. After they moved away, Nao grew apathetic and guilty about molesting Haruka. Upon their return, she attempts to rekindle their former close relationship. Sora Kasugano (Nao's former best friend) harbors great resentment towards her because Sora thinks that she will steal Haruka away after she saw the pair having sex on that summer day when they were younger.
She explained that she was troubled by her parents' constant arguing in the house and wanted to release her tension. She also clarifies that she cannot just find anybody to have that kind of relationship with.
After reconciling with Haruka, Sora discovered their relationship by finding the two making love. She expelled Nao from their house and ordered Nao to never talk to Haruka again. Nao is desolate after that and, though she wants to see Haruka, has to hide because Sora is always with him. After school, Haruka meets up with Nao at the grocery store. He tells her that he intends to make things right and to keep making her smile and she decided to stay optimistic to whatever Sora will say to her. The next morning, Nao comes over to pick them up for school. Sora seems to have calmed down a bit but continues to distance herself from them.
On the day they decided to go to the pool, Sora decided to follow them but Haruka nearly drowns. Sora sees Nao give mouth-to-mouth resurrection to Haruka. This caused Sora to try to be with Haruka all the time.
One afternoon, Haruka finds Sora missing after receiving a text from her saying "Let's leave here." Akira Amatsume, Kazuha Migiwa and Ryouhei Nakazato joins Nao and Haruka in search of her until, amidst the rain, Nao finds Sora at the bus stop. Refusing to go with Nao, Sora runs out of the bus stop, angrily telling her that she is the reason why Haruka has changed. Suddenly, a bolt of lightning strikes the bus stop and burst into flames. Sora then remembers she forgot her stuffed bunny inside. Nao rushes in to retrieve the only memento Sora has of her mother, causing her to be nearly trapped inside. After receiving the rescued item, Sora reveals to Nao her insecurities with her, that she is afraid Haruka would leave her alone. The next night, Sora joins everyone during the Summer Festival at the shrine. This time, Sora is more caring towards Nao.
- Ryouhei Nakazato
- Akira Amatsume
- Kazuha Migiwa
- Motoka Nogisaka
- Kozue Kuranaga
- Sora Kasugano (Nao took care of Haruka and Sora and they were close friends, but Sora saw Nao raping Haruka, which is the reason why Sora hates her)
- The name Nao means "apple tree" (奈) (na) and "thread" (緒) (o).
- Nao's surname Yorihime means "rely on, be dependent upon" (依) (yori) and "princess" (姫) (hime).
- Nao is the first of many characters to lose her virginity to Haruka Kasugano.
- Nao is one of few who approve of Haruka and Sora Kasugano's incestuous relationship.
- Nao is the only Yosuga no Sora character that use glasses.
- Nao is a child of parents whom struggle with marital problems.
- Nao is the only character who suffers from tension and turn to sources for release.
- Nao was one of many girls that Ryouhei Nakazato had his eye on, until Haruka told Ryouhei to leave her alone.