|Occupation||Student (grade 11)|
|Introduced In||The Dissociation of Haruhi Suzumiya|
|Last Appearance||The Surprise of Haruhi Suzumiya|
Sasaki is considered attractive; at least one student seem to prefer her to the beautiful Okamoto (Kyon was of this opinion but Sasaki disagreed), and Itsuki Koizumi described her as being able to "exude a charm that is able to mesmerize eight out of ten guys". (The latter created a problem when she met Haruhi Suzumiya in year 1, causing Haruhi to feel jealous.)
Sasaki went to the same elementary school as Haruhi Suzumiya. Afterward she changed her surname. She lives in the same area of town as Haruhi.
Kyon meets Sasaki in his third year of middle school; while he was initially familiar with her as a classmate, he did not know her intimately until they ended up in the same cram school class. Sasaki immediately notes that Kyon does not like his nickname because of the duration of the pauses he makes when he hears that name. She still calls Kyon by that name, however, because she believes Kyon's real name (which is still not revealed) is "royal and imposing". She says the phrase "yare yare" often when she's frustrated at Kyon, who took it and later uses it when he's in high school.
Sasaki and Kyon eventually walk to cram school/the bus station together, and end up having insightful conversations. Sasaki, like Haruhi, comes to believe love is like a mental illness, although Sasaki takes a more cynical view of love in believing it is a by-product of instinct that leads humans to reproduce (a "survival of the fittest" theory). Kyon notes that in contrast from when she speaks to girls, whenever she speaks to boys, instead of using the female "watashi" or "atashi" that she (or any other female) usually uses to refer to herself, she uses the male-reserved "boku", signifying that she sees all people as her peers and none as any different from her. This demeanor labels her as somewhat strange, leading to Kyon's reputation as having a liking for "weird girls".
When Sasaki hears of Kyon's fetish with supernatural beings, Sasaki contends that they cannot exist simply because even though logically a low probability would signify they could exist, logic does not work that way and thus it is impossible (an ironic statement considering that they do exist).
Moving the Universe
Sasaki eventually ends up going to an unnamed suburban high school with a high chance of going to university, at least this was Kyon's belief, but Sasaki did not confirm this. In the absence of Kyon, she meets Kyouko Tachibana, Kuyou Suou, and Fujiwara, none of whose full intentions are revealed besides Kyouko's. Tachibana believed that Sasaki was the true god, not Haruhi Suzumiya, and wished to transfer that power to her. However, Sasaki herself had little interest in this.
Kyon met Sasaki by chance between their first and second year of high school, while Kyon was on his way to meet the SOS Brigade. Sasaki introduced herself to Haruhi as an "old friend", and because of Sasaki's friendship with Kyon, Haruhi became jealous of her, thus triggering constant instability and several instances of closed space.
Shortly after school started, on a Saturday, Kyon ran into Sasaki again at the SOS Brigade's usual meeting place. Sasaki was accompanied by Kyouko Tachibana and Kuyou Suou. The rest of the SOS Brigade arrived very shortly afterward. Sasaki took her friends away, but gave Haruhi "advice" on how to handle Kyon on her way away.
Sasaki contacted Kyon by phone Saturday evening. She requested a meeting with between him and her associates, including the time-traveler guy on Sunday morning.
Kyouko Tachibana reveals to Kyon that Sasaki has similar powers to Haruhi, except that Sasaki is not only aware of her powers and those of her surrounding peers, but that also Sasaki has no desire to change anything about the world. Even Sasaki's version of closed space actually envelopes the whole world instead of just a certain area, is white instead of gray, and has no celestials (although Kyon notes they are devoid of any other change at all). Kyouko thus believes Sasaki is the "true" god, that Haruhi was a "mistake", and that with Kyon's assistance Haruhi's powers can be transplanted into Sasaki. Sasaki herself believes that she, as an introvert, does not want these powers, although Kyouko urges her to reconsider. The rest of the group didn't seem interested either. Kyon refused to assist, saying he could not, and the group broke up.
Kyon contacts Sasaki at the beginning of The Surprise of Haruhi Suzumiya and sets up an appointment. Sasaki, from a message alone, can tell that Kyon is "worked up", and advises him to be calm, because her supernatural companions may be wanting his anger from him.
The Tuesday after school, she caught up to Kyon as he left North High. They met at the cafe again. The meeting didn't go well. Fujiwara told Kyon that Kuyou Suou could stop Nagato's illness, but he would only tell her to do so if he consented to transferring Haruhi's power. Sasaki caught him in a lie (he had previously said it didn't matter who ended up with the power) and treated her rudely. Sasaki herself told Kyon not to fall for this kind of blackmail, and he resolved to leave the offer. Meanwhile, Kyouko Tachibana grew upset at Sasaki when she drifted into a philosophical conversation rather than sticking to the topic at hand. The meeting broke up, with only Kuyou Suou, Kyon and Sasaki remaining.
On Wednesday after school, Kyon found her at his house. She discussed philosophical motivations of aliens, but pointed out that Fujiwara and Tachibana were humans and so easier to understand. Fujiwara had admitted his plotting was about self-interest, and only cared about the end result, not how it was done.
Sasaki left feeling better having chatted with Kyon, and he was left with new resolve to take on his opponents.
On Thursday, she contacted Kyon, letting him know Fujiwara wanted another meeting, in front of the train station. She said Fujiwara was serious this time. A big event involving Mikuru Asahina was coming up. She told Kyon he would have to finally decide which girl, her or Haruhi, would be normal.
After school the next day Sasaki, Kyouko Tachibana and Fujiwara met up with Kyon. They took a taxi to North High. During the trip, Fujiwara again antagonized Sasaki.
The school was enveloped in Sasaki's closed space some time after they entered it.
Sasaki's closed space somehow merged with Haruhi's closed space as well. This empowered Itsuki Koizumi, enabling him to cow Fujiwara into obedience.
Afterward Sasaki thanked Kyon for preventing her from becoming a god-like being. She talked about how much she misses talking with Kyon during their middle school days and reveals that she was asked out a little while ago. Being in shock, she couldn't give an answer. Wanting to talk about it with Kyon, she came over to his house on Wednesday. They then parted with Kyon resolving to say "Hey again, close friend" when they next met.
Like Haruhi, Sasaki can create closed space, although its properties are different, appearing as a white void where nothing changes. Her own espers have abilities within this space. No celestials were observed.
In the β timeline, Koizumi said that Sasaki often makes a fixed quantity of closed spaces, but doesn't let them run out of control.
The Disappearance of Nagato Yuki-chan
In The Disappearance of Nagato Yuki-chan Sasaki's relationship with Kyon makes Nagato jealous. Because they became close in junior high, Kunikida thought that Sasaki and Kyon were going out. For the most part, she retains a lot of her original personality. However, unlike the main universe, she does not openly dismiss romantic feelings.
In this series, Sasaki goes to Kouyouen, which, like in the Disappearance arc, is a co-ed school. There, a boy earnestly confessed to her, but Sasaki didn't know how respond to him. She first used this as an excuse to ask Kyon to pose as her boyfriend for an undetermined length of time, but he refused stating a girl (Nagato) had already confessed to him. With this, she firmly told the boy that she was not interested in him, saying that there was already someone she had feelings for. This implies that Sasaki was probably, at least in part, attempting to see if there was any chance of a deepening relationship with Kyon.