Also note that there are unmarked spoilers for the novel series as of this writingnote , so if you've only watched the anime, you might still be getting spoilers for future seasons.
- Full-Name Basis: Anyone with a full name is almost always supernatural in some way. The rest have either No Full Name Given, or No Name Given at all. The exceptions are Fujiwara, the time traveler who refuses to give his real name and just picks an obvious pseudonym; Sasaki, a girl and old friend of Kyon who can create closed space of her own and has espers of her own; Miyoko Yoshimura, Kyon's sister's friend, nicknamed Miyokichi, who has not manifested any supernatural powers; Nakagawa, Kyon's former classmate and tight end for his high school's American football club, who had the ability to perceive the Data Overmind by looking at one of its interfaces, but mistook it for love when he set eyes upon Yuki; and certain members of the Agency who have not yet manifested supernatural powers but have full names given.
- Invisible Parents:
- No one seems to have parents, although this is justified in the case of Mikuru and the Humanoid Interfaces. Kyon's mother is mentioned, but she never appears on-screen (although both of his parents are on the first page of the manga).
- Taniguchi's dad is mentioned in Disappearance.
- Haruhi's parents are also mentioned (Melancholy V and the preview for book 10), we just never get to meet them.
- Also understandable with Itsuki because he IS a transfer student.
- Tsuruya mentions her father several times in Intuition.
- Secret Identity: Four out of five SOS Brigade members, as well as all the other Aliens, Time Travelers, and Espers out there.
Ryoko Asakura is the Class Representative of Kyon's class. She's described as a model student — hardworking, beautiful and smart, until she gets revealed as another alien data interface, the same as Yuki. She's gotten tired of sitting around and observing until Haruhi acts, and so she decides to act... by stabbing Kyon and seeing how Haruhi will react. Kyon is saved by Yuki, who then proceeds to shut down Ryoko. This convinces Kyon that Yuki is an actual alien.
Interestingly, she has a good twin in The Disappearance of Nagato Yuki-chan; a dimension where she is Yuki's best friend and genuinely tries to help her be with Kyon. Although she is just a little bit jealous (of Kyon), she tries to hide that.
- Big Ol' Eyebrows: Among the largest of the cast, male and female.
- Bitch in Sheep's Clothing: It can kind of be argued either way; on the one hand, when dealing with the vast majority of people, she seems to be legitimately, actually nice and to even enjoy it, doubly so in Disapperance's Alternate Universe and its related spinoff (which, given the nature of The 'Verse, may or may not count, depending). Her interactions with Kyon, however, run the gamut; she starts out nice, then there's the big stabbing incident, then a lot of her lines with him in Disapperance straddle the line between "good-natured ribbing about Yuki" and "passive-aggressive bitchiness", then she stabs him for real, and then in Book 10, she saves his life while holding a knife to his throat at the same time. Perhaps it's most accurate to say that if she has an Inner Bitch, Kyon brings it out, and since he's our narrator, we may get a disproportionate view of it. Granted, she also seems to bitch out Kimidori a bit, but by Book 10 she has nearly as much of a legitimate axe to grind with the Data Overmind as Yuki does at this point, so it comes across as less "self-righteous bitchiness" and more "you really don't have any room to tell me what I should and shouldn't be, Nagato understands that".
- Class Rep: Popular and the class president.
- Combat Tentacles: Those glowing appendages she forms are described as such at least by Kyon.
- Cute and Psycho: She smiles happily while trying to stab a guy to death. Even after coming back from Yuki's deletion. Her kernel must be built around stabbing people or something.
- The Dreaded: She is easily the person who scares Kyon the most, due in no small part to being the only character who tried to kill him specifically (and came pretty damn close, too). Disappearance does an excellent job of underlying just how pants-wettingly terrified he is when she walks through the door.
- Evil Counterpart: To Yuki: in Disappearance, Kyon outright calls her Yuki's "shadow" after Asakura stabs him, and in the 10th novel, she even claims that she'll exist so long as Yuki does.
- Eviler than Thou:
- Kuyo Suo of "the Anti-SOS Brigade" is even more deranged than Ryoko.
- Also, her human counterpart from "Disappearance" is much worse than normal Ryoko. Normal Ryoko's attempt to kill Kyon was motivated out of psychotic pragmatism and there was no real malice behind it. The alternate Ryoko, on the other hand, was motivated by emotional spite, and she came much closer to killing him than normal Ryoko did.
- Faux Affably Evil: Admittedly she's more Blue-and-Orange Morality than out-and-out evil, but certainly her cheerful personality is only skin-deep.
- Flirty Voice Ploy: Ryoko uses a flirty tone when asking Kyon to be the go between for Haruhi and the class.Ryoko: Pretty please.
- Girl with Psycho Weapon: Truly insane and dangerous weapons.
- Girly Bruiser: She's a bubbly girly girl who is a very skillful fighter and almost killed Kyon.
- Girly Girl with a Tomboy Streak: She's very girly, being a Valley Girl in her school, but she also fights and isn't fazed with blood.
- Go-Karting with Bowser: When she isn't stabbing people, she's legitimately kind, empathic and helpful (even if she rags on Kyon sometimes). Kyon even sits down to an extended dinner with her in Disappearance (partially at Yuki's insistence), and rather manages to enjoy himself despite his paranoia about being knifed out of the blue. The fact that she appears in Disappearance at all is telling. Yuki temporarily stole Haruhi's Reality Warping powers, which means that she very easily could have fabricated a universe where Ryoko didn't exist at all; in fact, she would have to know how negatively Kyon views her, and this was all done for his sake. That Yuki brought Ryoko back regardless really suggests that Yuki must see something redeeming in her.
- Graceful Loser: At her final moments while shutting down, she smiles and tells Kyon to enjoy life with Haruhi.
- Hime Cut: Straight hair with two sidelocks and somewhat even bangs. She likely added this to her Inferface's appearance to give herself a respectable air as the Class Rep.
- Homoerotic Subtext: Starting in Disappearance she starts showing a weird fixation on Yuki, though some of it may be a result of Yuki restructuring the world. It's really hard to interpret her behavior properly considering how, well, alien she is. Perhaps it's a mix of If You Ever Do Anything to Hurt Her... and I Want My Beloved to Be Happy.
- Improbable Weapon User: A subversion of this. She uses a mundane weapon, which is pretty odd if you think about it. In the anime she uses a survival knife(note the top serrations, it's not detailed as much in the novels). This knife is primarily intended as a tool rather than a weapon. In short, she uses an improbably mundane weapon.
- Let's Get Dangerous!: "Shifting to Termination Mode."
- Mask of Sanity: Seems like a nice popular girl, but truly insane.
- Nominal Hero: As of Book 10. She's still the same Asakura, she just happens to be fighting on the same side as the Brigade now.
- Not Quite Dead: Twice.
- Psychopathic Woman Child: Insane with a girly voice.
- Refused by the Call: Near the beginning, Haruhi asks for aliens, among others, to join her. Ryoko, being in Haruhi's class and hearing Haruhi's request, seemed perfect for Haruhi, being an alien and quite willing to engage and befriend Haruhi. However much Ryoko tries to join Haruhi, though, Haruhi doesn't even acknowledge Ryoko's existence until Ryoko "transfers out" to Canada. Haruhi rejects Ryoko in favor of Yuki, despite Yuki not being in the same class and apparently not even making any attempt to contact Haruhi directly. Kyon lampshades this fact in Surprise.
- Summon Magic: Invoked by Ryoko in Surprise when she tells Kyon that he can call her at any time and she will appear, after just saving his life in like fashion—only, Kyon doesn't remember ever summoning her.
- Token Evil Teammate: Fills Haruhi's shoes in that role, although Haruhi was actually more antagonistic than evil until her Heel–Face Turn in Sigh left a void that Asakura would eventually fill in Surprise Vol. 1.
- Tomboyand Girly Girl: Girly Girl to Haruhi's, Yuki's, and Tsuruya's tomboys.
- Unresolved Sexual Tension: With Kyon, of all people. Especially given the... imagery involved. He really, really tries to avoid acknowledging this in the 10th novel, straight down to refusing to look at her... because he doesn't want to admit to himself that she's attractive and that looking at her might allow him to begin to forgive her, a trap he fell into already in "Disappearance."
- Villainous Rescue: Saves Kyon from Kuyo in the 10th novel.
- Well-Intentioned Extremist: All Ryoko wants to do is to break the status quo and incite some reaction from the titular character. Her method happens to be trying to murder the narrator, and major love interest, Kyon. When she returns in the tenth novel as a Boxed Crook, she still wants to kill Kyon because she still believes that her actions were justified. Still, she protects him, because she wants to be the one to kill him.
Mikuru's future self who appears several times to Kyon.
- Anti-Hero: She can be quite morally ambiguous and manipulative at times.
- Femme Fatale: More obvious than her younger version.
- Fiery Redhead: Inverted; she has red hair like her present-day self, but while she's become more competent and self-confident, she's also very calm most of the time.
- Future Badass: Maybe not badass, but Mikuru's future self is rather competent and self-confident, compared to her younger self. On the downside, she's a lot less morally clear.
- Grew a Spine: The once shy and fragile girl is shown to be very self-confident in the future.
- The Handler: Her role in Intrigues, to the point that Intrigues reads much like a spy novel. The differing layers of classification (after all, not even the younger Mikuru knows that her own future self is her direct superior) and the overall atmosphere of secrecy gives the time travelers' faction the feel of an espionage agency, and as their field representative Adult Mikuru is responsible for much of that atmosphere.
- Light Feminine and Dark Feminine: Dark Feminine to her younger self's Light Feminine.
- Took a Level in Jerkass: Scheme reveals that the once Nice Girl will grow up to be one of the more manipulative characters of the series (even to the point of abusing her younger self) unless, as hinted at in the Sequel Hook in Surprise Vol. 2, Kyon can prove Fujiwara wrong on the subject of whether history can indeed be changed.
- Transhuman: In Disappearance she reveals that she has a non-physical computer integrated with her brain, and that her time-travel device is likewise a part of her.
- Unscrupulous Hero: If not outright evil.
No one really knows what's up with Tsuruya-san, Mikuru's classmate, ersatz SOS Brigade member and something of a Sixth Ranger. She's got the (ankle length) green hair one would expect from a Humanoid Interface, but seems to be totally normal, if just as much of a Genki Girl as Haruhi. She's also notable for her Cute Little Fang, Big Fancy House, tendency to point and laugh (very loudly), and for inspiring the Fan Webcomic and Memetic Mutation Sensation, Churuya. She also seems unusually aware of the SOS Brigade's oddities for a Muggle, but seems content to enjoy the show rather than disrupt the Brigade's attempts to keep Haruhi under control.
- Attention Deficit... Ooh, Shiny!: She is, needless to say, quite distractable (and hyper).
- Big Fancy House: A traditional Japanese home that takes up an entire block. Then there's their ski house, which is slightly more sane, but still huge.
- Cool Big Sis: In age and attitude; she dotes on her younger friends as if she is their big sister.
- Crouching Moron, Hidden Badass: Although she isn't "special" enough to be an official member, she is well aware of the abnormalities around the SOS Brigade. She can quickly grasp the situation while at the same time be tactful enough to keep Haruhi and herself out of the loop.
- Cute Little Fangs: One at a time, but it flips from one side of her mouth to the other depending on the scene.
- Dissonant Laughter: She laughs at all times—even during The Sigh of Haruhi Suzumiya when Mikuru is drunk. That scene was treated like something out of a horror movie, except for Tsuruya's laughter. But even she shuts up when Kyon tries to punch Haruhi.
- For Happiness: Tsuruya states that this is her purpose, to ensure the happiness of others while remaining out of the spotlight.
- Genki Girl: She manages to out-genki Haruhi.
- Giving Someone the Pointer Finger: Tends to do this when she laughs.
- Hero of Another Story: Itsuki implies that she's off having her own adventures; her family is "very influential" in the Esper community, even though she's not one.
- The Hyena: Once she finds something funny, it's hard to make her stop laughing. She's not big on subtlety either. She won't just laugh, she'll point and laugh. There's one single occasion where she gets serious. Since it's Tsuruya, this only helps to increase the drama and tension.
- Motor Mouth: She generally enters a scene by asking a million questions, then hopping off to ask someone else a million questions, all before waiting for a single answer.
- Nice Girl: Will be friends with anyone, unless they hurt Mikuru.
- No Full Name Given: Only her family name is known.
- Ojou: She doesn't act like it, but she's filthy rich. Her family is one of the backers for Itsuki's Organization.
- O.O.C. Is Serious Business: When she's not laughing when Haruhi abuses Mikuru during "The Sigh".
- Saying Sound Effects Out Loud: Her Verbal Tic of "nyoro" is essentially this, as it means "tilde", which is often used in Japanese text as an extension of a syllable to give a drawn-out or playful pronunciation.
- Ship Tease: With Kunikida in Book 11. Kyon notes that she'd probably like the kind of guy who would strive to become as smart as her just to be able to go to the same school.
- The Tease: She likes "suggesting" things to Kyon. Like recommending he stay overnight at her guest house with Mikuru. Of course, she's only kidding, and Kyon doesn't fall for it.
- Token Rich Student: She's from a very rich family, but she still goes to a high school that's mentioned to be rather average in regards to academics and seems to be largely made up of students from middle-class backgrounds.
- Tomboy and Girly Girl: Tomboy to Mikuru's Girly Girl. Shares this status with Haruhi.
- Tomboy with a Girly Streak: Athletic and bold like Haruhi, but way more hyper. A tomboy proud of her long hair and doesn't mind a maid outfit.
- Verbal Tic: "Nyoronote " though she only says it very rarely (once in the anime). The anime also adds "megas"; though it's used only once in the actual anime it appears in her Image Songs.
Emiri Kimidori is a mysterious student in North High and a Mysterious Watcher to the Brigade. She is revealed to be a humanoid interface just like Yuki, but does very little, save for a couple of minor plots and being an ally to the Student Council President.
- Adaptation-Induced Plot Hole: More regarding characterization. The Image Songs for the anime's first season were released prior to the tenth volume of the light novels; building off the fact that she's an interface, Kimidori's song "fixed mind" portrays her as someone reaching for humanity and wanting to participate in the fun everyone else has but being unable to. The tenth volume, however, reveals that she doesn't give a damn about anything that interferes with what the Entity wants, not even Yuki's personal safety.
- All-Powerful Bystander: Of the first and last variety at the same time: she hasn't been ordered to help out Nagato when she gets sick in the tenth novel, and she doesn't care enough about her to do so either. Thus, she just continues to watch.
- I Just Want to Be Normal: According to her Image Song. However, in the novels this turns out to be a case of Canon Marches On, since she appears to actually be largely indifferent to humans and is strictly loyal to the Entity.
- Kick the Dog: She says it's not her place to look after Yuki when she's in trouble, and generally has little care whether Yuki lives or dies.
- Mysterious Watcher: Essentially the role given to her. She refuses to act outside of this.
One of Those Two Guys and Kyon's main non-SOS Brigade friend. Both totally normal to all appearances, Taniguchi is a Big Eater and something of a teenage Casanova Wannabe who is implied to have dated Haruhi for exactly five minutes back in junior high.
- Breakout Character: To some extent. Enough to get his own image songs in season 2, at least. And he gets alot of scenes extended or added to the movie.
- Casanova Wannabe: Oh boy. Rates all the girls in school on an A-F scale meticulously, and flirts with them a lot too. Accumulates years worth of experience with a success rate of zero.
- Chekhov's Gunman: In Disappearance, he mentions he's looking for girls from Kouyouen Academy, and in Intrigues it's implied that he got together with one and that she broke up with him. That girl was Kuyou Suou, who mistook him for Kyon.
- Did We Just Have Tea with Cthulhu?: Taniguchi briefly tasted Haruhi's shortest relationship, listed one alien as a top pick, then dated another one for four months. Fortunately for his sanity, he's Locked Out of the Loop and just a Romantic False Lead.
- Genki Girl: Or rather, Genki Boy, as he is very energetic, as lampshaded by Kyon asking him to 'rub some of his energy onto me (Kyon) sometime'
One of Those Two Guys, Kunikida is Kyon and Sasaki's junior high friend, and receives no Character Development or Backstory detail whatsoever - except that he gets better grades than Taniguchi or Kyon. They both act as an anchor of normalcy for Kyon, and occasional extra bodies in the SOS Brigade for things like baseball games or magazine publishing.
- Hyper-Awareness: In Surprise, Kunikida is able to at least notice that Yuki Nagato and Kuyou Suou aren't what they seem, noting that he senses an "inhuman aura" from them.
- Sensitive Guy and Manly Man: Sensitive Guy Kunikida who is quite passive compared to Taniguchi who is loud and reckless.
- Shipper on Deck: For Kyon x Sasaki. (In the novels at least.)
- Ship Tease: He to North High so he can be with Tsuruya more often.
- Those Two Guys: He is one of Kyons other friends, and but in the background than Taniguchi
Kyon's Little Sister
Kyon's Little Sister, known only as Imouto-chan, is a chipper little kid who occasionally tags along on her brother's sort-of-adventures, being a bit hyper but still better-mannered than most Annoying Younger Siblings. Since their parents seem to leave them to their own devices, she forms the core of Kyon's family life in the novels, and as Kyon's home life doesn't get much attention she is mostly seen with her brother outside the house.
- Annoying Younger Sibling: To Kyon, sometimes. As is often so in real life, not a view held by anyone else.
- Captain Obvious: "Kyon-kun, your phone".
- Cheerful Child: She's generally an innocent, happy-go-lucky girl. She often acts younger than her age, cares more about having fun with things than actually learning to do them properly (like the time Kyon notes that she seems to be enjoying herself trying to ski even though she’s falling down every five seconds), and is liable to spontaneously start singing to herself or the cat at completely random moments. The only thing that ever seems to upset her is being left behind when Kyon goes on a trip.
- Cuteness Proximity: Turns to mush around Shamisen, always wanting to pet him and play with him and sing little songs to him. May also explain why she enjoys being around the girls in the SOS Brigade too, especially Mikuru.
- Genki Girl: A milder version than Haruhi and Tsuruya, but she definitely qualifies. She’s very energetic, especially when she’s excited about something, she’s full of confidence and determination (though usually without the talent to back it up), and she loves to talk. Kyon notes that her outbursts of hyperactivity often end with him carrying her because she’s worn herself out and fallen asleep.
- Little Stowaway: She tries to hide in Kyon's duffel bag when he's packing for the Brigade's Remote Island trip, but he quickly discovers her when he picks up the bag and notices it's much heavier than it should be. In the book he makes her stay home, but in the anime she's allowed to come along anyway.
- Locked Out of the Loop: While she tags along with the SOS Brigade from time to time, she doesn't know anything about the members' true natures and she's managed to avoid getting caught up in any of their more serious adventures. Kyon is happy to keep it that way.
- The Nicknamer: "Kyon-kun" for Kyon, "Shami" for Shamisen, "Miyokichi" for her friend Miyoko Yoshimura, and "Haru-nyan" for Haruhi. She's the only other person besides Kyon and Tsuruya who ever addresses Haruhi informally, and while she didn't invent the nickname "Kyon" for her brother, she is the one responsible for spreading it around to everyone else.
- No Name Given: Kyon and all of his friends never call her anything except Imouto-chan (Little Sister).
- Sixth Ranger: She is one of the people who joins in Brigade activities from time to time when they need more hands on deck. Lampshaded by Kyon in "Snowy Mountain Syndrome," when he notes that she's basically a junior Brigade member as far as Haruhi is concerned.
- Super-Strong Child: Played for laughs in the anime, and especially the movie version of Disappearance. She isn't strong enough to hit a baseball more than five feet without the help of Nagato's magic baseball bat, but she has no trouble physically hauling her 16-year-old brother out of bed and dumping him on the floor every morning to wake him up.
- Tagalong Kid:
- Invoked in "The Boredom of Haruhi Suzumiya" – Kyon doesn't want the SOS Brigade to win their baseball game, so he deliberately brings his little sister along to play with them because he knows she's a terrible player and is more likely to hurt their their chances of winning than help.
- Subverted in the "Remote Island Syndrome" short story. She tries to tag along on the trip, but Kyon catches her and sends her home.
- Defied in the "Remote Island Syndrome" anime adaptation and in "Snowy Mountain Syndrome." She is allowed to tag along on the trips, but both times she has other people babysitting her and keeping her safely out of the way when the SOS Brigade get caught up in the real adventure.
- Lampshaded by Haruhi in "Where Did The Cat Go?" during the game of fukuwarai. Kyon's sister was again an uninvited tag-along, but Haruhi says that she knew she would join them, and pulls out another game sheet that she drew for her before they left.
- Token Mini-Moe: Downplayed; while she's a cute little girl who's the youngest member of the cast, she isn't sexualized in any way, appears only sparingly (though she tends to appear with the main cast more often in the anime's merchandising), never steals the spotlight when she does appear, and annoys the hero because she acts her age.
The Computer Club President
A nameless character who is the president of the Computer Society. His role in the plot is essentially The Chew Toy, being the subject of several of Haruhi's antics — being blackmailed into giving away computers to the SOS Brigade, getting taken over by a cricket-like Data Entity, etc. He declares himself and his club to be rivals to the SOS Brigade and challenges them to a game of their own creation, but they lose and become "vassals" to the SOS Brigade. Emiri Kimidori also pretended to be his girlfriend. It must suck to be him.
- Butt-Monkey: He's tipically on the receiving end of Haruhi's crazy antics when he's around.
- Defiant to the End: In Day of Sagittarius he screams "Glory to the Computer Club!" when his ship is destroyed.
- Defeat Means Friendship: After getting "subjugated", the Computer Club has been on good terms with the SOS Brigade and sometimes gives support in the Brigade's activities. He even wishes Yuki to become his successor.
- Dynamic Entry: The receiver of it once he declares the Computer Society to be the SOS Brigade's rivals.
- Large Ham
- Laser-Guided Karma: After he and his boys try to cheat their way to victory in their game against the SOS Brigade, Yuki manages to one-up them by hijacking the code to their game so as to prevent them from cheating.
- No Name Given: The anime at least, plays with this by making Kimidori say his name, only to get cut off by the meowing of a cat.
- Once Done, Never Forgotten: Everyone remembers how Haruhi blackmailed him into giving the SOS Brigade computers...except for Haruhi herself.
Another character with No Name Given, he is the school's Student Council President introduced in The Indignation of Haruhi Suzumiya by Koizumi to give Haruhi an antagonist and to keep her from getting bored. He acts like Four Eyes, Zero Soul in his role as the president, but he is secretly laughing at how ridiculous his job is. Later on, it seems that Haruhi's influence is making him take his job more seriously.
- Armor-Piercing Question: Delivers one to Haruhi in Indignation. Kyon notes that few people have that ability.Student Council President: If I had something to be proud of, it would be that I am in this position as the result of a fair election. And so, how did you come to be sitting on that seat? Oh, honorable Brigade Chief?
- Becoming the Mask: He comments that he slips back into his mask every now and then, even when Haruhi isn't around. He seems unconcerned, but is warned against this trope by mask master Koizumi himself.
- Corrupt Politician: Both as a facade and in reality, albeit on a high school scale. To the SOS Brigade, he is a bully abusing his authority to destroy the Brigade. In reality, he kicked out all other members of the Student Council except Kimidori and intends to use the Student Council fund for his own interests.
- Full-Name Basis: Or a Japanese variant thereon: he always addresses female students with the honorific "-kun," which is typically used for boys and young men. As That Other Wiki notes, there are two exceptions to that practice, "in business settings, young female employees may also be addressed as -kun by older males of senior status," and "in the Diet of Japan (Legislature), chairpersons use -kun when addressing diet members and ministers." Either way, he's being pretentious.
- Student Council President: Invoked by Koizumi to keep Haruhi entertained.
Formally introduced in Surprise (having made her first nameless appearance in Dissociation), Yasumi Watahashi is one of the new first years at North High participating in Haruhi's rigorous SOS Brigade entrance tests. Kyon notices her among the other first years as the only one interested in Haruhi's lecture on the history of the SOS Brigade.
- Deus ex Machina: Literally, she was created by Haruhi's subconcious precisely in order to handily solve the plot.
- Even the Girls Want Her: Mikuru certainly does.
- Have We Met Yet?: Kyon recognizes her from somewhere, but cannot for the life of him remember where. In the Beta timeline, she runs into him in the clubroom and notes that she hadn't met that version yet.
- Foreshadowing: Loads.
- She greets Kyon on the phone with "It's me, ME." This is him mishearing her name; "Watahashi" sounds a lot like "watashi." So she was actually saying "It's me, Watahashi." Kyon notes that only Haruhi could get away with "It's me;" she is Haruhi.
- The official English translation of Dissociation manages to preserve this: rather than having her emphasize "watashi," Yasumi instead spells out the word "me" ("It's M-E, me") — said out loud, it sounds like the tail end of her first name, Yasumi, which keeps the sense that Kyon was mishearing her.
- She manages to keep up with Haruhi in a marathon, which should be literally impossible. Because she is Haruhi.
- Every single member of the club instantly loves her, even Yuki. While for the others it was likely unconscious, Yuki was almost certainly well aware of who and what she was.
- After being told that Kyon made the SOS Brigade website and that she should fix it, she goes into a rant about what a horrible job he did, and that she'd expect a middle-schooler to do better. Sounds exactly like the kind of thing Haruhi would say.
- She greets Kyon on the phone with "It's me, ME." This is him mishearing her name; "Watahashi" sounds a lot like "watashi." So she was actually saying "It's me, Watahashi." Kyon notes that only Haruhi could get away with "It's me;" she is Haruhi.
- Genki Girl: Her energy even gets on Haruhi's nerves.
- Literal Split Personality: To Haruhi, which explains why Kyon finds her so familiar.
- Moe: In-Universe, even Mikuru can't stand how adorable she is.
- Moe Anthropomorphism: Of Haruhi's subconscious self.
- Moment Killer: Deliberately interrupts Sasaki's meetings with Kyon, even though Sasaki couldn't bring herself to confess to Kyon the first time around.
- Significant Anagram: When her name is read in the proper reading (Yasumizu Watahashi), it can be rearranged to say watashi wa(ha) Suzumiya — I am Suzumiya.
- Sixth Ranger: Albeit briefly.
- Stalker with a Crush: To Kyon. She calls him before they ever meet, and shows up at his house completely unannounced to play with his sister. He's disturbed, despite her being quite blase and low-key about it, and doesn't understand why she doesn't see it as a big deal. Actually, she was helping keep the timelines synched by performing Sasaki's actions from the Beta timeline in the Alpha. She does appear once in the Beta timeline by "accident," apparently just to see how he's doing.
- Tomboy and Girly Girl: Girly girl counterpart to her tomboyish foil, Haruhi.
T is a foreign exchange student in Kyon and Haruhi's class, and a member of the Mystery Research Club. She's a big fan of mystery novels and borrows books from Yuki on occasion.
- Childhood Friends: With Tsuruya.
- I Have Many Names: Aside from her real name, she is known as "T" to her classmates and is called "Lie" by Tsuruya.
- The Nicknamer: She has trouble pronouncing Japanese names, so she tends to give people nicknames, such as calling Kyon "Kyam," Haruhi "Haru," and Koizumi "Ikki."
- Ojou: Like Tsuruya, she is from a rich family.
- Only Known by Initials: Sort of. T isn't so much an initial but rather a nickname that came from her first name.
- Only Known by Their Nickname: The entire class calls her T because Ottilie Adrastea Hohenstaufen-Baumgartner is very long and hard to pronounce.
Shamisen is an everyday alley cat (or maybe not...) who becomes a Touched By Haruhi Talking Animal for a while when playing Yuki's familiar in the Adventures of Mikuru Asahina student film. He's actually quite The Philosopher when he can speak. He loses this ability after the film is finished and the weirdness starts to wear off, but he becomes involved in a few other adventures after Kyon and his sister adopt him. He is also a male calico.
- Contemplate Our Navels: He's awfully philosophical, at times when he can speak.
- Meaningful Name: Shamisen (the instruments) use cat skin in their construction.
- Unusually Uninteresting Sight: He's a male calico cat. Kyon mentally comments on this. This is possible (though very rare) in real life, due to males with the XXY chromosome set. However, this also probably means that Shamisen is sterile.
A distant relative of Itsuki's, who apparently made his fortune in biotechnology, and offered his island villa to the Brigade for a vacation. Actually a member of Itsuki's Organization, and probably not even related to him.
- The Driver: During his appearance in Intrigues, he drives a cop car with the skill that can only come from lots of experience.
- Faking the Dead: Twice, once at the Remote Island and once on the Snowy Mountain. He put significantly more effort into it the first time.Keiichi: Hello. I've been stabbed again.
Haruhi: Who killed you?
Keiichi: I can't say. I'm dead.
- Psychic Powers: As a member of the Organization with a full name, he's implied to be an esper, but that hasn't actually been confirmed.
- Self-Made Man: His cover. It might even be true.
Keiichi's younger brother, who killed him at the Remote Island. Not really, of course; it was all part of the show. He's a member of Itsuki's Organization, and it's unclear if he's even related to Yutaka.
- Accidental Murder: The script for Remote Island claimed that he got into an argument with his brother and accidentally stabbed him.
- Impersonating an Officer: His appearance in Intrigues. Though Mori lampshades the fact that Kyon has no way of knowing if he's a fake or a real cop.
- Psychic Powers: As a member of the Organization with a full name, he's implied to be an esper, but that hasn't actually been confirmed.
The butler working for Yutaka Tamaru on his island villa. In reality, he's a member of Itsuki's Organization.
- The Driver: His appearance in Intrigues involves him driving the car chasing Mikuru's kidnappers, and Kyon even wonders if he's the one who drove the black cab Itsuki is occasionally seen riding around in.
- The Team Normal: Due to the way names are used to indicate powers in this series, the fact that he only has one name implies he is not an esper, unlike the rest of the team, but neither his lack of powers nor his teammates' having powers is confirmed.
- Papa Wolf: He is dangerously calm when Mikuru is kidnapped, and Kyon notes that he acts like she is his own grand-daughter.
The maid working for Yutaka Tamaru on his island villa. Of course, she's not actually a maid, but a member of Itsuki's Organization.
- Meido: She's a prim and proper Western maid. Not really, of course, but she does a very good job of faking it.
- Alternately, she actually is a maid when not performing her duties for the Organization.
- Psychic Powers: As a member of the Organization with a full name, she's implied to be an esper, but that hasn't actually been confirmed.
- Vague Age: Kyon's pretty sure she's older than him (judging by the fact that she can drive), but other than that, it's hard to pin her down.
The Anti-SOS Brigade
The "Anti-SOS Brigade" are The Psycho Rangers. While not nearly as cohesive as Kyon's True Companions, they've more or less allied for differing reasons.
Kyon's old girlfriend. Or at least the female person he used to hang around with, and the reason for his pre-Haruhi reputation for "liking weird girls." Sasaki is intelligent and analytical... but chooses not to do anything to change her environment. She knows about aliens, time-travelers and espers, which are interesting, but she's not going to change her daily routine over it. She's somewhat of The Spock and wishes to keep out of the God-business all the organizations have.
- A-Cup Angst: A one-off comment from her in Rainy Day, where she expresses a hint of jealousy upon the idea of Kyon ogling the popular girl in their class and her larger "assets".
- Anti-Villain: Seemingly a Type I but really a Type IV.
- Character Catchphrase: "Yare yare", at least in the past. Yes, she's the one Kyon picked that up from.
- Chekhov's Gunman: She was mentioned offhand multiple times as Kyon's precedent for liking weird girls (even before most of the characters were introduced), and her name appears in Kyon's phone in the Disappearance movie (screenshots◊ here◊); she doesn't actually appear until the ninth novel.
- Contemplate Our Navels: This habit of hers can easily rival Itsuki's.
- Evil Counterpart: To Haruhi, in that she's the god analogue, but also to Kyon in that she's pretty much just a normal person being dragged along for the ride. Her philosophical ramblings have a lot in common with Koizumi, as well.
- Forgotten Childhood Friend: To Kyon and Haruhi.
- Good All Along: Though she's introduced as Haruhi's Evil Counterpart, she's actually the only member of her group who isn't villainous at all. In fact, she was even a friend of Haruhi's back in elementary school! She and Kyon hatch a plan to stop the rest of the Anti-SOS Brigade. It wouldn't have worked, but it's the thought that counts.
- I Just Want to Have Friends: She mentions that one of the reasons she hangs around the Anti-SOS Brigade is that they're the only people who talk to her. In the end, Kyouko states that she wishes to remain Sasaki's friend, and Kyon promises to always be her friend too, so things work out well for her.
- Meaningful Rename: She notes that her family name was different in elementary school, but it was changed for some reason. This is why Haruhi didn't recognize her.
- New Old Flame: Suddenly introduced as Kyon's 'close friend' in the ninth novel, but was foreshadowed in the first novel.
- Refusal of the Call: She tells Kyoko she wants nothing to do with Haruhi's power.
- Stop Worshipping Me: Unlike the relationship between Haruhi and Koizumi (where he merely theorizes she is a god as a hypothetical scenario), Kyoko very strongly believes that Sasaki is god, and furthermore deserves to be. Sasaki, on the other hand, thinks Kyoko would be much happier if they were just friends.
- Suspiciously Specific Denial: Feels the need to bring up the topic again and again to remind Not Love Interest Kyon (and herself) that about the She Is Not My Girlfriend.
- Token Good Teammate: Just as Haruhi was once the Token Antagonistic Teammate to the SOS Brigade, so is Sasaki this to the Anti-SOS Brigade, eventually to the point of actively trying to sabotage Fujiwara's goals with the help of Kyon and Yasumi.
- Tomboy and Girly Girl: Girly Girl to Haruhi's Tomboy. Ironically, she's the one that refers to herself using male pronouns, though it actually depends on who she's talking to (i.e. the gender of the other party is proportional to the gender of her first-person pronouns).
- Unwitting Pawn: To the rest of her group, but especially Fujiwara. She was one of a few, however, to exactly know she was the group's pawn and secretly worked to stop it.
An Esper who believes that Sasaki should be God. Reveals that in Sasaki's Closed Space, nothing changes. Ever. She also believes that Kyon has the power to transfer the power from Haruhi to Sasaki.
- Evil Counterpart: To Itsuki, as an esper. But in personality she more resembles Mikuru, being gentle, kind, and having no idea what is really going on.
- Reformed, but Rejected: Though she seems to genuinely regret being a part of the whole kidnapping Mikuru/Michiru thing, Kyon still doesn't trust her because of it.
- Ship Tease: With Itsuki at the end of Novel 11.
- Touched by Vorlons: As with the other Espers. Her powers, however, came from Sasaki.
- Wham Line: Delivers the main one in Dissociation: "We believe the existence of the real god is not Miss Suzumiya, but Miss Sasaki."
An agent of the rival to the Data Overmind: the Canopy Domain. Has far, far less social skills than Yuki; she seems rather unaware of anyone's existence. Has a lot of dark hair which is commented on, possibly a reference to the Stringy-Haired Ghost Girl trope.
- Artificial Human: She is an interface, after all.
- Blue-and-Orange Morality: Does not understand morality. All she knows is that she wants to communicate, but doesn't know what it actually means to communicate or to fully grasp what other entities are. Since she goes about it in such incomprehensible ways, it leaves her extremely dangerous.
- Creepy Monotone: Unlike Yuki's, hers is legitimately creepy.
- Eerie Pale-Skinned Brunette: Combined with her design and personality, she definitely gives off this vibe.
- Evil Counterpart: To Yuki. Unlike the other members of her team, she's a straight parallel with only one counterpart. She's pretty much Yuki but without any of her positive qualities and with all of her negative traits taken to highly unsettling degrees.
- Eviler than Thou: She's worse than Ryoko Asakura AND Emiri Kimidori, although her definition of evil might be difficult.
- Humanoid Abomination: She has the appearance of a human girl, but everything about her behavior is described as being very alien and unnatural. The only thing that can be discerned from her actions is that she wants to communicate, but her alien morality means she has no idea how.
- Kill the God: Serves as an accomplice to an attempted one.
- Memento MacGuffin: The only mildly humanizing element to her character is the fact that she kept the watch Taniguchi gave her, and even thanks him for it when she sees him again.
- No Social Skills: Not played humorously either. She is so mentally alien that she literally has no idea how living things, let alone humans, act.
- School Uniforms are the New Black: Like Yuki, she doesn't seem to wear anything else.
- Shadow Archetype: To Yuki; she's essentially what Yuki would be like if she had even fewer social skills and absolutely no idea how regular humans interact or behave, and as a result she's even more unsettling and alien than Yuki could ever be.
- Starfish Language: Implied at first, and then subverted. The reason why she doesn't know how to communicate with humans is because the Canopy Domain did not, in fact, really know what communication even was, meaning they had no language.
- Stealth Pun: When Kyon asks if the Canopy Domain means overhead, Yuki points North, while sitting at North High.
- Technically a Smile: As Kyon puts it, "the perfect simulation of a smile."
- Uncanny Valley Girl: Everything about her just screams that there's just something wrong about her.
- When She Smiles: Subverted; her smile is beautiful, but it's just not right.
Kyon believes this name to merely be a pseudonym, so he is commonly referred to as "that sneering bastard". The most villainous of the group, he is a Time Traveller who believes that Time Travel actually makes humans slaves to Causality.
- Big Bad: Of "Intrigues of Haruhi Suzumiya", and also ends up as "Surprise of Haruhi Suzumiya"'s one too.
- Evil Counterpart: To Mikuru as an evil time traveler, but he also closely resembles Koizumi in appearance and action; Kyon himself describes him as literally an "evil Koizumi". He even has some elements of Kyon, being detached from the rest of his group, yet also something of the leader.
- Have We Met Yet?: To Mikuru in Novel 7.
- Kill the God: Goes out of his way to make a very serious attempt on Haruhi's life at the climax of Surprise Vol. 2.
- Killed Off for Real: Apparently by Itsuki in the 11th book. They fight, an explosion is seen, and then the way people speak of Fujiwara afterward seem to indicate that he's long gone. Of course, given his nature as a time-traveller, there's always the possibility a Fujiwara from a different point in time could decide to drop in...
- Long-Lost Relative: In Novel 11, it's revealed that Mikuru is Fujiwara's elder sister (well, he claims it to be, but it seems that he isn't her brother anymore due to alterations to the timestream).
- Knight Templar: He pretty much drops all claims to well-intentioned extremism after he tries to kill Haruhi.
- No Name Given: For a while, he eschews names, and only adopts an obvious pseudonym at the insistence of the rest of the Anti-SOS Brigade.
- Screw Destiny: He wants to prove that the future isn't dependent on predetermined events. He's right... maybe.
- Smug Smiler: His perpetual expression is described as "an evil version of Koizumi's smile."