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social ineptitude and unpleasant personality.Despite being incredibly anti-social, she craves the companionship and attention of others. She suffers from a raging superiority complex, vivid delusions of grandeur, intense self-loathing, and social anxiety so severe that she can barely get out a sentence when talking to someone she is not intimately acquainted with.The dark circles under her eyes are genetic (and shared by her brother).
- A-Cup Angst: It's not apparent as most examples of this trope, but it's there.
- Adorkable: In spades, when her Jerkass tendencies aren't in play.
- All Girls Want Bad Boys: Although she doesn't actually hook up with a "bad boy", she seems to be fond of Bastard Boyfriend characters, as evidenced by her enjoyment of a drama CD about Yandere boys.
- Ambiguously Bi: Has pretty obvious sexual lust for Yuu, as well as being shown enjoying the memory of a stranger's panties. That said, she's constantly trying to get with boys, including her own brother, and she enjoys Otome Games as well as Bastard Boyfriend characters. Amusingly, while thinking about what it would be like to be with another girl, Tomoko thinks that her harassment of Yuu is totally normal. It could be argued that Tomoko has been very confused by all those H-Games she's played. In chapter 51, she sees her lust after Yuu as something natural and normal, and so too her Big Brother Attraction towards Tomoki, but she doesn't actively think about getting with girls the way she does about getting a boyfriend, or see herself as a lesbian... until it's a chance to be popular.
- Annoying Younger Sibling: Acts like one for Tomoki despite actually being older. According to the volume 5 omake, it was her obnoxiousness that caused their once-loving relationship to turn sour. On the other hand, one What If? omake shows that he would end up disliking her even if she were to remain kind to him.
- Butt Monkey: Any of her attempts to become popular always come out wrong for her.
- Character Development: Albeit slowly. By her second year, she's dialing down her schemes to become "popular" and noticed by everyone, just aiming to befriend and talk to people. She's also become more comfortable at cafés and other public places. She also doesn't stutter as much when talking to people she doesn't know. However, she's also reignited an old feud with a middle-school classmate who ended up in the same school as her. Interestingly enough, during the second year school trip arc, she gets even more sociable than before.
- Chronic Villainy: She's never managed to break her bad habit of doing Jerkass things.
- Clingy Jealous Girl: When it comes to Yuu or her brother, the latter of which she declared if he ever brought home a girl, she would take responsibility and kill her.
- Conveniently Seated: At first, she seats in the back row seat by the window. When the second semester and Tomoko loses her seat, she lampshades it by commenting about how lucky she was getting "the seat main characters always get in anime and light-novels" in the first period, lamenting that she now has to dwell in an awkward spot, surrounded by people.
- Cosmic Plaything: She doesn't realize it, which might be a good thing as the truth might plunge her into the pit of despair or worse, since she can't realize why her attempts to make friends are massive failures.
- Covert Pervert: Played with; since the viewers are always privy to her thoughts, it's easy for us to see that she's very perverted, but most other characters (aside from Tomoki) are unaware of how perverted she really is.
- Creepy Shadowed Undereyes/Exhausted Eye Bags: Seems to be a family trait; however, Tomoko's habit of staying up late at night probably doesn't help, as she notes before trying on glasses to hide them.
- Desperately Craves Affection: To the point of making Brother-Sister Incest overtures, with Tomoki none too pleased. Also part of why she's so attached to her only real friend, Yuu.
- Determinator: Despite the universe doing everything it can to make her give up.
- Don't You Dare Pity Me!: As shown in chapters 33 and 42, she doesn't like it when others take pity on her, as she feels patronized by this.
- Eerie Pale-Skinned Brunette: The bags under her eyes only serve to further emphasize this aspect of hers.
- The Eeyore: She falls into bouts of self-loathing and has a lot of negative thoughts in social situations.
- Expy/Distaff Counterpart: Downplayed very hard. An otaku Loser Protagonist who's a master of Dating Sims and near-zero communication skills? Sounds a lot like a gender-flipped fusion of Keima Katsuragi and Tatsuhiro Satou. But unlike Keima, who's a loner by choice and is perfectly capable of dating real girls in much the same way as fictional ones (given enough encouragement, or coercion for that matter), or Satou, who eventually outgrew his Hikikomori ways, Tomoko repeatedly fails at socializing in real life.
- Failure Hero/Failure Is the Only Option: Done rather well. She can't do anything right. Every time she has a goal, it's bound to fail or backfire horribly.
- The few Throw the Dog a Bone moments she gets are usually down to luck and the kindness of others, or when she's not actually trying so hard to become popular.
- Female Misogynist: Her jealousy leads to a general resentment of other girls aside from Yuu, often viewing girls who are more socially adept than her as "bitches" or "sluts".
- Foolish Sibling, Responsible Sibling: The Foolish to Tomoki's Responsible.
- Friend to All Children: She's fond of kids and enjoys their company. This is Played for Drama, since it serves as a reminder that she doesn't have any friends of her own age.
- Gamer Chick: Effortlessly plays a Pop'N Music knockoff with only a blank stare on her face, not to mention her constant playing of otome games.
- Gonk: Often, when emotional.
- There was also the time where she tried to change her appearance, which worked out well until she decided to mess with her face.
- Green-Eyed Monster: She enjoys the misfortune of others and frequently wishes for horrible things to happen to people that she perceives as having happy, carefree lives. She also does have big green eyes, and calls girls more socially successful than herself, including her best friend Yuu, "bitches", "sluts", etc.Tomoko: "If you're not a worthless god, I'd like to see you try and make me happy... If you can't manage that, at least make everyone as unhappy as me. If you can't, it's fine I guess... But I'll despise you forever..."
- Also why she couldn't get along with Kotomi in middle-school despite being much alike, as she wanted to keep Yuu to herself.
- As of chapter 97 she seems to have realized that her former classmates who are more sociable than her don't act sociable to spite her, and she doesn't hate them for this anymore.
- Hollywood Nerd: Mostly averted. She's an introverted shut-in, with the disheveled appearance and complete lack of social skills to highlight it. In a departure from the archetype, she's also not particularly accomplished academically.
- Hypocrite: She angrily denounces anyone more popular than her as shallow, vapid and selfish, and refers to any girls more sociable than her as "sluts". She's the real shallow and selfish one, who seeks popularity above all else, and proclaims: "Without doing anything, I can get into the pants of the boys for three years!" in the very first chapter.
- I Just Want to Have Friends: ...and get laid, apparently.
- As the series progresses, there's a subtle development in that Tomoko's goal moves down from "getting popular" to just "making a friend", and at the very least "talking to people".
- Ineffectual Death Threat: Frequently wishes death and worse on her classmates for the smallest of offences, like someone apparently taking her umbrella.
- Inferiority Superiority Complex: While she's rather self-centered and looks down on a lot of people for petty reasons, it's still clear that her self-esteem is actually very, very low.
- Inner Monologue: Keeps her thoughts to herself more often than actually speaking.
- In-Series Nickname: "Mokocchi"
- Ironic Name: Depending on what kanji you spell it with, the name "Tomoko" can mean "beautiful girl" or "wise child", among others. Needless to say, she's neither of these things.
- Jerkass: Downplayed. In the main series, she can come off as a condescending jackass who can occasionally show humility and self-esteem, although she most often keeps her negativity to herself. However, Tomoki and Komiyama tend to see and feel the more unpleasant side of Tomoko.
- Little Big Sister: She's considerably shorter than her younger brother. Not very unusual given he's only a year younger, but it still highlights her immaturity.
- Loners Are Freaks: Her mindset, which she desperately wants to avoid.
- Loser Protagonist: Though, she tries hard to not be this.
- Manipulative Bastard: She tries. Dear lord, she tries.
- Meaningful Name: "Kuroki" can literally mean "black mood". It sums up her character pretty well.
- Nerds Are Virgins: Several storylines are about Tomoko's lack of experience and sexual frustration.
- Never My Fault: Zigzagged. She often derides herself and finds faults with her social skills and appearance, but never dwells on it and immediately finds something else to blame for her social failings.
- No Social Skills: Pretty much the entire conflict of the plot is based around the fact that Tomoko's skills leave a lot to be desired.
- Otaku: Of Otome games. So much that she attempts to socialize in real life with tactics from the games. See the Expy/Distaff Counterpart entry for details.
- Otaku Surrogate: Downplayed; while she does have interests in anime and video games that male otaku in real life would have, she's also into things that are aimed specifically at girls, such as otome games. Unfortunately, her interests in all the perverted media aimed at otaku only make her more unapproachable and unable to function in social situations.
- Peek-a-Bangs: Although both of her eyes can occasionally be seen, this trope is largely in play for her through much of the series.
- Person as Verb: In Chapter 39, she tries to stand out more in her class by performing a wacky introduction during the first day of second year. For her efforts, among her classmates, her name becomes a synonym for doing something exceptionally poorly. Fortunately, it seems to have gone out of fashion by Chapter 42.
- Playboy Bunny: Dresses as one in a fantasy sequence that's a Shout-Out to Haruhi Suzumiya. She somehow manages to make it look ugly and unappealing.
- The Quiet One: She once went a month and a half without talking to anyone outside her family — her streak was broken when she managed to tell her teacher "goodbye". Ironically, her inner monologues are highly eloquent.
- She's All Grown Up: A page in the anthology reveals that she could grow up to be quite pretty.
- Shrinking Violet: Combined with No Social Skills, this is the reason she can barely put together a full sentence with anyone she doesn't know.
- Sibling Yin-Yang: With Tomoki.
- Sitcom Arch-Nemesis: With Komiyama, whom Tomoko dislikes because she feels that she has to compete with her over Yuu's attention, as well as because Komiyama is romantically and sexually interested in Tomoki, causing Tomoko to be disgusted with her, and, as of chapter 47 of the main story, also because Komiyama admitted that she didn't like Tomoko back in middle school.
- Tomato in the Mirror: Chapter 1: After 5 months trying to convince herself that she's popular, Tomoko literally sees herself at the mirror and admits the horrible truth:Now that I look in the mirror after a few years, I see that I turned into some creepy entity!
- The Unfavorite: Played with. Her mom loves both her and Tomoki equally, but is often exasperated at her daughter for being lazy and irresponsible. This causes Tomoko to become slightly resentful whenever her mom praises Tomoki for his maturity and self-reliance.
- The Unsmile: Pretty much every attempt she makes at smiling ends up coming off as looking more like a Slasher Smile. Combined with her Creepy Shadowed Undereyes, the effect is... rather unsettling.
- Unsympathetic Comedy Protagonist: Her portrayal switches between this, Cosmic Plaything and some combination of both depending on the chapter. She can be very pitiable, but at the same time rather self-centered, condescending (especially to her classmates, though this is restricted to her Inner Monologues and never expressed outwardly) and, in Chapter 33, is shown to be a devotee of schadenfreude. In the spinoff, she's portrayed much more unsympathetically than in the main story.
- Wide Eyes and Shrunken Irises: She has this expression a lot.
- Wrong Genre Savvy: One of the major factors behind her inability to adapt to society is the fact that she tends to "learn" social skills through anime and video games, and mistakes many character interactions therein (including those that are, from an objective viewpoint, downright outlandish) for actual practice, and tries to emulate them in real life, which more often than not only serves to further humiliate her.
- You Are What You Hate: The reason she despises Kotomi. Both are antisocial and their Only Friend is Yuu. Each one of them believes the other is below her.
- The Ace: In comparison to Tomoko, at least. He's mature, reliable, athletic, has a large social circle, and multiple girls that are interested in him.
- Annoying Younger Sibling: Played with. He does tend to get on Tomoko's nerves, though not so much due to obnoxiousness as due to the fact that he's guilty of such "crimes" as staying home sick while Tomoko has to go to school, having friends who care enough to visit him while he's sick, or cleaning his own room and making his lunch himself (much to their mother's praise - and unlike his sister, and thus making her look bad in comparison). Also inverted, as Tomoki definitely sees Tomoko as his annoying older sibling.
- Berserk Button: While he always braces himself whenever his sister approaches him, he gets particularly angry at her when she barges into his room unannounced, which is frequently.
- Big Little Brother: He's considerably taller and than his older sister. While it's not particularly strange, as they're only one year apart and both teenagers, it emphasizes how down-to-earth and mature he is in comparison to her.
- Covert Pervert: Subverted. Tomoko constantly accuses him of being Caught With His Pants Down whenever she enters his room, but he's always shown to simply be listening to music, reading a book or sleeping. Likewise, whenever Tomoko accuses him of being attracted to her, he expresses disgust and confusion about why she would even suggest it. Later, when forced to sit down and have lunch with Kotomi and Akari by Tomoko, it's made pretty clear that he simply isn't particularly interested in having a girlfriend.
- Clueless Chick Magnet: In addition to Tomoko making Brother-Sister Incest overtures, both Kotomi and Akari pine for him. He barely even remembers they exist, remains oblivious to their feelings even after they both blurt out in his presence that they would like to see his dick, and shows no interest in romance in general.
- Deadpan Snarker: In response to Tomoko's antics.
- Exhausted Eye Bags: Like his mother and sister, although their mother's are less pronounced.
- Expy: Of sorts to Kyousuke Kousaka.
- Face of a Thug: Interestingly, while he has this look, he's still fairly popular at his school, since he seems to have regular friends and two girls bring him the class printout when he gets sick.
- Face Palm of Doom: When ticked off, he simply grips his sister's head really hard.
- Father, I Want to Marry My Brother: In a home video their mom found in episode 7, he said as a little kid he wanted to marry Tomoko. He was notably disturbed when he saw this video (also because of how much more affectionate he was towards her).
- Foolish Sibling, Responsible Sibling: The Responsible to Tomoko's Foolish.
- Hidden Depths: Generally comes off as a grouchy loner, though this is almost entirely because we almost only ever get to see him when he's forced to put up with Tomoko's obnoxious antics. On the occasions where we get to see his life outside of his sister, he is shown to be a surprisingly popular guy with a large friend group, multiple female admirers and an active spot on his school's soccer team.
- I Have No Sister: Exclusively refers to Tomoko as "that girl", even in his own thoughts. This is in stark contrast to when he was young, where he affectionately called her "nee-chan".
- Jerk with a Heart of Gold: Tends to physically rein in his sister if needed. That said, deep down he is a generally good-natured guy who is shown to be perfectly nice and friendly when dealing with people who aren't his sister.
- Not So Different: Subverted in Chapter 41. Tomoko visits him in his classroom and sees him sitting alone and by himself; this gives her the impression that he is a loner just like her. However, when she visits him later she finds out that he is actually very popular in class and has not only friends but also admirers. Tomoko doesn't take the revelation well.
- The One Guy: Currently the only major male character. Justified due to Tomoko having problems working up the courage to talk to other girls, let alone guys. This is briefly lampshaded when, after realizing that she has begun interacting with other girls more frequently, Tomoko vows to try to talk to a guy, only to awkwardly barge into Tomoki's room, wave at him and then leave.
- Ordinary High-School Student: All evidence points to him having a perfectly normal and fulfilling school life, in contrast to his sister.
- Perpetual Frowner: He's always wearing a grumpy expression of some sort, at least when around his sister.
- Pet the Dog: Sometimes he takes pity on Tomoko.
- The Power of Hate: Thinking about various occasions when Tomoko has pissed him off causes him to tap into an Unstoppable Rage that has allowed him to become the star player of his soccer team. In comparison, thinking about the few occasions when the two of them have actually gotten along causes him to be thrown off his game and miss scoring the winning goal.
- Sibling Yin-Yang: With Tomoko.
- Straight Man: Serves as this whenever he shares a scene with his sister.
- Tranquil Fury: While he's frequently pissed off at his sister, he only explodes at her when she's being particularly obnoxious. Otherwise he remains fairly stoic when dealing with her.
- Would Hit a Girl: He's not above lashing out when Tomoko's getting on his nerves (giving her a kick, grabbing her face, etc.). He invoked the other trope one time Tomoko was annoying him. Then when her antics went too far, he had no choice but to strike her into calming down.
- Attention Deficit... Ooh, Shiny!: In the final episode of the anime, she starts to chase after a distraught Tomoko out of concern for her but ends up being distracted by a cat.
- Beautiful All Along: An interesting case where she's introduced after having this already happen to her. Back in middle school she wore thick glasses and unflattering clothing, but was still beatiful underneath them.
- Beware the Nice Ones: After embarassingly winning a bet in the Christmas special of 2016 Yuu makes Tomoko and Komiyama sing Christmas carols together for an hour.
- Brainless Beauty: Despite her beauty and kindness, she's oblivious to Tomoko's unsavory nature and has below average grades. In the second Christmas special Tomoko opines that even using Twitter or keeping a blog would be too complicated for Yuu to handle. She also remains oblivious to the animosity between Tomoko and Kotomi until chapter 54 of the main story.
- Closet Geek: She's currently this, due to her popularity having soared at her high school after she cleaned up her appearance. At one point she says that she's happy that she can still hang out with Tomoko since she doesn't have anyone else to talk to about anime-related things.
- Cool Pet: In chapter 64, while catching bugs with Tomoko and Kotomi, she manages to catch a rhinoceros beetle. Tomoko and Kotomi comment on its coolness and rarity, and Tomoko convinces Yuu to keep it as a pet.
- Covert Pervert: One thing she isn't oblivious about is innuendo.
- Decoy Protagonist: In the spin-off she is set up as the protagonist at first, but the narrative focus eventually moves from her to Tomoko and Komiyama, and the story is mostly about the two's "friendship".
- Dumb Blonde: Her hair is dyed, but otherwise applies.
- Erotic Dream: Implied in chapter 7 of the spin-off. Tomoko and Kotomi are pretty delighted by it.
- Even the Girls Want Her: Tomoko and Kotomi both have pretty obvious crushes on her in middle school and separate high schools have done little to ebb their lust.
- Foil: To Tomoko, also to Kotomi. She had been, initially, shy like her two friends but was able to overcome it and build a social life, unlike Tomoko. In middle school she already had a hidden natural beauty that drew attention. Most importantly, she has shown negative feelings towards other people the least, unlike her friends.
- The Glasses Gotta Go: After taking her glasses off, her popularity soared.
- Green-Eyed Monster: Surprisingly, in chapter 57! She deals with it in a completely different way than Tomoko, though.
- The Heart: She is pretty much the only reason Tomoko and Kotomi even talk to each other, and also the only reason they are willing to be civil when they do talk. In chapter 54 she takes an active role to the trope.
- Innocently Insensitive: Her casual remarks indicating that she has a much more fulfilling social life than Tomoko can hope for, including having a boyfriend, cause Tomoko a lot of distress.
- Komiyama was also hit with this, in chapter 6 of the spin-off.
- During Tomoko's, Yuu's and Kotomi's Christmas party in the 2016 Christmas special Tomoko comes up with the idea for the trio to buy one another funny gifts that would be completely useless to the recipient rather than ordinary Christmas gifts. In response Yuu buys Tomoko a pack of condoms. Yuu claims to have thought about it simply as a funny gift, and is embarrassed when Tomoko points out what such a gift implies about what Yuu thinks of Tomoko.
- Meganekko: Wore glasses in middle school. Still wears them at home.
- Ms. Fanservice: Or at least this is how Tomoko sees her.
- Nice Girl: Overall, a pretty nice and sweet (if somewhat airheaded) person.
- Oblivious to Love: Doesn't notice Tomoko's crush on her.
- Only Friend: To Tomoko, who even admits this in one of her Inner Monologues in chapter 29.
- Opaque Nerd Glasses: In anime flashbacks, though her eyes are visible in both manga.
- Otaku: She was this during middle school. Now that she's in high school and has a better social life, she's more of a Closet Otaku around everyone except Tomoko and Kotomi, whom she feels she can be more open about otaku-related things with.
- Rapunzel Hair: In middle school.
- Stupid Good: Her niceness can be very high when it comes to her friends. For example, when they were in the pool:Tomoko: "If I peed in here, would you pull away from me?"
Yuu: "I wouldn't. Because we're friends."
- Zettai Ryouiki: Type A, when wearing her school uniform and working at her uncle's cafe.
Voiced by: Kaori MizuhashiOne of Yuu's old middle-school friends. She immediately takes a dislike to Tomoko, who sees Kotomi as a rival for Yuu's attention. Unfortunately, Kotomi proves to be just as passive-aggressive and anti-social as Tomoko.Kotomi is formally introduced in the spin-off manga It's Your Fault My Friend's Not Popular, and later on she is re-introduced in the main series. Kotomi does not appear in the anime as it only adapts stories from before her first appearance. However, she appears in a special OVA, bundled with the Japanese release of the main series's seventh volume.
- A-Cup Angst: Just like Tomoko.
- Alliterative Name: Both her first and last name begin with "K".
- Ascended Extra: She first appeared in Tomoko's flashback to her middle-school years in Chapter 30 of the main series as the third, unnamed girl running the the marathon with Tomoko and Yuu; she's only seen in three frames and has no speaking lines. In the spin-off series, starting with Chapter 2, she is one of the main characters. She then makes her formal debut in the main manga in Chapter 46.
- Berserk Button: Badmouthing her crush Tomoki, as Tomoko found out in chapter 54.
- Bookworm: Always shown reading a book during her job as the school librarian.
- Butt Monkey: Not only is her crush on Tomoki unrequited, as he barely knows she even exists, but the plots revolving around said crush tend to end with her in some embarrassing situation or otherwise miserable.
- Covert Pervert: Revealed to be one in Chapter 7 of the spin-off, though she is in denial about it. Also, in chapter 91 of the main series she blurts out that she is interested in Tomoki's dick... in Tomoki's presence, no less. As of chapter 101 she seems to have accepted that this is a part of her personality.
- Cross-Popping Veins: When Tomoko pisses her off. Which is often.
- Foil: To Tomoko. She's basically her but more proper looking and with more common sense.
- Friendly Rivalry: With Akari. They both pine for Tomoki, but so far there seems to be no animosity between the two, and Kotomi actually seems to care about Akari's well-being a bit. Kotomi encourages Akari to be honest about her feelings for Tomoki in chapter 101, and later, in chapter 108, she hesitates whether to tell Akari that Tomoki greeted her, because she didn't want to rub it in Akari's face. Akari, in turn, wanted to badmouth Kotomi when asked about her by Tomoki, but backed off when she realized that Kotomi's feelings for Tomoki are the same as her own. In chapter 112 they are even shown preparing the Valentine's Day chocolates together.
- Game of Nerds: Her conversations with Tomoko and Yuu in Chapter 4 and 9 of the spin-off show that she is a baseball fan.
- Green-Eyed Monster: In chapter 83 she is distraught by the revelation that she has a romantic rival who is also interested in pursuing Tomoki (something Tomoko gleefully takes advantage of to troll her).
- Impossibly Tacky Clothes: In a clothes store she hinted an interest for cosplaying. In chapter 79 she looks like the new protagonist of a Final Fantasy game. Averted on the beach trip, because Yuu chose her bathing suit.
- In-Series Nickname: "Komi-something". Also: "Glasses". Both given by Tomoko.
- Fan Nickname: Many fans use those nicknames.
- Love Makes You Crazy and Love Makes You Dumb: Tends to lose her common sense and act irrationally whenever the plot involves her crush Tomoki in some way.
- Meganekko: Is actually a cute girl with glasses.
- My Parents Are Dead: Has revealed that her father died from an illness when she was five. Yuu gets awkward, Tomoko... not much.
- Not So Different: Apparently neither she nor Tomoko had any friends in their class before befriending Yuu. She and Tomoko both like the same anime, got the same type of hairstyle in Chapter 3 of the spin-off, got insecure with Yuu's beauty in Chapter 4, found themselves unable to talk to guys and ended up in the same high school. Chapters 47 and 48 of the main manga show her walking home from school alone and eating her lunch in the bathroom, implying that she doesn't have many - possibly even any - friends in high school either. Notably this does not make them less hostile towards each other at all.
- Their Not So Different nature is even lampshaded by the title of one of the 4-Komas from Chapter 7 of the spin-off, "Cut from the same cloth".
- They appear to be showing some small progress when it comes to getting along. They accept having to hang together to be with Yuu during Summer break, and chapter 71 shows them taking a picture together (though it was played off as awkward).
- According to chapter 83 their similarity even extends to their appearance (at least whenever Kotomi is distraught and without glasses) as they get mistaken for each other (albeit by someone who had little prior contact with either of them.
- One could think that chapter's 83 title ("Because I'm Not Popular, I'll Tell Lies") was referring to Tomoko. While Tomoko does tell an obvious troll lie in the chapter, it is Komiyama who says the more significant lies.
- Only Sane Woman: Has more common sense than her two friends, at least in matters not related to her crush Tomoki or potential romantic rivals.
- Opaque Nerd Glasses: Sometimes she is presented like this depending on the situation. Her glasses are a little variant of this trope because they are not so big.
- Precision F-Strike:"Shithead."
- Right in Front of Me: In Chapter 2 of the spin-off she tried to break the ice with Tomoko by telling her a story about having a laugh in the previous year when she heard that some middle schooler was still riding a bike with training wheels. Guess who that middle schooler was?
- Sitcom Arch-Nemesis: With Tomoko. She dislikes Tomoko because the latter tends to act like a Jerkass towards her for reasons she can't fathom, and only ever strikes back at her when provoked.
- Stalker with a Crush: Acts like this towards Tomoki in some chapters, though this is Played for Laughs. In chapter 88 she is shown taking photos of him during the athletics meet, getting turned on when he is made to wear baseball uniform and hoping he would be wearing the kind of uniform where the understocking is showing. In the very next chapter, when let into Tomoki's room by Tomoko, she considers looking through his drawers or his trash before deciding to lie in his bed instead.
- Unknown Rival: When they reunite in Chapter 46 of the main story, Tomoko has forgotten about Kotomi. On the other hand, Kotomi bears a grudge against Tomoko. (The next chapter reveals that they didn't spend all of their middle-school years in the same class.) Now both are aware of the other's dislike.
- Vitriolic Best Buds: With Tomoko on their best of days, particularly past Chapter 57. On their worst, it's a Sitcom Arch-Nemesis relationship.
- Wide Eyes and Shrunken Irises: When she is surprised and/or angry.
- With Friends Like These...: Yuu is the only link that makes her and Tomoko tolerate each other.
- You Are What You Hate: The reason she despises Tomoko. Both are antisocial and their Only Friend is Yuu. Each one of them believes the other is below her.
Voiced by: Rie Kugimiya (Japanese), Juliet Simmons (English)Tomoko and Tomoki's thirteen-year-old cousin and a seventh-grade schoolgirl. Having been fed a steady stream of face-saving lies by Tomoko, she idolises her older cousin.
- Audience Surrogate: Her reaction to Tomoko's card game.
- Broken Pedestal: How she sees Tomoko after all her attempts to look cool backfires spectacularly on her. Unlike other examples though, she takes the revelation well, and the next time they meet her admiration is replaced not with utter disdain, but with pity and appreciation that at least she tried her best.
- Cloudcuckoolander: How Tomoko sees her in later chapters. In particular in chapter 104 Tomoko gets disturbed after listening to Kii gushing about Tomoko making her heart skip a bit, and also later, while watching Kii play an otome game for the first time (as Kii goes out of her way to keep all her stats average and make characters in the game neither hate not like her with a precision that Tomoko considers robotic). Kii is also completely oblivious to how uncomfortable her attempts take care of Tomoko and "help" her find a boyfriend make Tomoko.
- Death Glare: Pulled one mixed with a Thousand-Yard Stare when she was angry with Tomoko, also..."No! Just take it."
- This has become a regular expression for her when she is angry, with an added Stepford Smile.
- Innocently Insensitive: She means well when she tries to take care of Tomoko after finding out the truth about her, but so far her actions just drive it home to Tomoko how pathetic she has gotten.
- Nice Girl: An unusual role for a Type-A Tsundere specialist like Rie Kugimiya. She's so nice she doesn't harbor any grudge against Tomoko for unwittingly breaking her good impression of her.
- Only Known by Their Nickname: Until chapter 60, where it's revealed that her name is Kiko.
- Replacement Goldfish: In chapter 60 Tomoko speculates that Kii tries to take care of her because she treats her as a replacement for her deceased dog. At the end of that chapter Kii even gives Tomoko that dog's hairpin (the one she is always wearing).
- Token Mini-Moe
Voiced by: Ai Nonaka (Japanese), Juliet Simmons (English)President of Tomoko's (and later Tomoki's) student council.
- Early-Bird Cameo: In the anime, when she replaces the random girl holding the stack of papers that Tomoko accidentally runs into. Downplayed because this first appearance is an earlier part of the chapter/episode she would appear in.
- Nice Girl: Some female students mention that she's popular with both boys and girls at the school due to her helpfulness. She is noticably kind and even protective toward Tomoko.
- Student Council President
- Throw the Dog a Bone: She does this frequently for Tomoko. Seeing Tomoko down after Yuu leaves at the end of the school festival, Megumi borrows a mascot costume and gives her a hug and a balloon. In Episode 12, she also mentions having to keep an eye on that "cute girl" after Tomoko ends up getting flustered out of trying to strike up a conversation with her after a gust of wind gave her a good view of Megumi's panties.
Voiced by: Yūko Kurose (Japanese), Margaret McDonald (English)Tomoko's classmate and the first person in Tomoko's class that Tomoko is able to talk to on a semi-regular basis.
- Ascended Extra: Appears as a background character as early as chapter 4 of the manga/the first episode of the anime. She becomes a recurring character starting with chapter 39.
- Bitch in Sheep's Clothing: While she was the first person to make an effort to talk to Tomoko semi-regularly, and generally comes off as a polite and friendly person, Tomoko's efforts to get closer to her reveal that she is quite callous. Despite being nice to Tomoko, she still clearly looks down on her as an outcast and has no desire to be friends with her, to the point of cheerfully insulting her attempts at making conversation.
- Closet Geek: Likes Slice of Life anime and wishes to be a voice actress, which she hides from her friends. In chapter 97 she tells Tomoko they can talk about anime from time to time, but only in secret.
- Forgotten First Meeting: Chapter 110 reveals that she and Tomoko took their high school entrance exam together, and afterwards even talked briefly and fist bumped. However, Tomoko ignored Hina when she was trying to introduce herself. Zig-zagged, as Tomoko remembers the meeting itself, but not that the girl she met was Hina.
- Nice Girl: Notably, she seems to be the only person in Tomoko's class (other than Yuri in later chapters) who sometimes goes out of her way to strike up a conversation with Tomoko.
- Unwanted Assistance: On two occasions her well-meaning attempts to reach out to Tomoko ended rather poorly for Tomoko:
- In chapter 39, when the time comes for Tomoko to introduce herself at the first day of her second year, it turns out that Hina not only thought that Tomoko's introduction at the beginning of the first year was great, but also told everyone about it, and thus everyone in the class is looking forward to another great introduction. This causes Tomoko to panic and publicly embarrass herself.
- In chapter 43, Hina gets curious about what Tomoko is searching the Internet for on her phone (during class) and asks Tomoko about this. This startles Tomoko so much that she drops her phone and it ends up in their teacher's hands with some NSFW images still onscreen.
Voiced by: Sanae Nakata (Japanese), Beth Lazarou (English)Tomoko's P.E. teacher. During Tomoko's second year she becomes Tomoko's homeroom teacher.
- Adults Are Useless: Zig-zagged. She is one of the few people who actually notices how isolated Tomoko is in her class, questions her about it and tries to help her. Unfortunately, so far her efforts to help Tomoko make friends fail due to her bluntness and mostly just put Tomoko in more awkward situations. Ogino grouping Tomoko with Yoshida, Yuri and Ucchi for a school trip did result in Tomoko's social circle expanding a bit, as after the school trip she does occasionally interact with Yoshida and Yuri, but even that turned out to be a mixed blessing at best (that's especially true of Tomoko's "acquaintance" with Yoshida).
- Ascended Extra: Made her first, brief appearances in chapters 10 and 25 of the manga. Once she became Tomoko's homeroom teacher she was also given a larger role in the story.
- Boyish Short Hair: Makes her look androgynous as a result.
- Cannot Keep a Secret: Zig-zagged. She likes to spill out her students' secrets as long as she doesn't mention their names.
- Unwanted Assistance: Tomoko's opinion on her attempts to help her make friends. Hina didn't seem thrilled about Ogino helping her prepare for her future career as a voice actress, either.
A girl with blonde hair and a bad temper that Tomoko has a habit of pissing off.
- Berserk Button: When first introduced she has two: 1) perverted acts in general, especially being groped, and 2) being called a delinquent. Tomoko being Tomoko, she manages to repeatedly hit both these buttons, and it seems she is becoming yet another Berserk Button for Yoshida.
- Delinquent Hair: She's a bleached blonde.
- Face of a Thug: Certainly looks like a standard delinquent girl, but is heavily suggested to simply be an ordinary girl who is into punk fashion that Tomoko just assumes is a delinquent.
- Flanderization: Early chapters portrayed her as an ordinary girl with a Face of a Thug who Tomoko was exceptionally good at pissing off. By the latest chapters, she seems to possess a Hair-Trigger Temper that can be set off by basically anything, regardless of who or what they are. She also generally yells and swears with much more frequency.
- Girls Love Stuffed Animals: She seems to have an affinity for cute things in general.
- Goofy Print Underwear: Tomoko mentions that she wears Hello Kitty-print panties.
- Hair-Trigger Temper: She is always quick to threaten or even hit Tomoko, sometimes with little provocation. On the other hand she doesn't act like this when interacting with other characters, so maybe it's just that Tomoko is really good at hitting her Berserk Buttons. Notably, in chapter 106 she does not lash out at her friend who called her a moron to her face.
- Hidden Depths: Despite what Tomoko thinks of her, she is shown to like cute things, couldn't recognize a love hotel when ever other character could and apparently plans to celebrate her Coming of Age Day in Disneyland.
- Hot-Blooded: The angry type.
- Japanese Delinquents: Invoked in-universe, as Tomoko is completely convinced Yoshida is a delinquent. As Tomoko was repeatedly shown to be Wrong Genre Savvy, this may or may not be correct.
- Jerk with a Heart of Gold: While she's generally angry and annoyed, this is mostly because she is justifiably pissed off at Tomoko for saying or doing something insensitive to her. Otherwise, she is shown to be a relatively pleasant person who seems to actually like Tomoko to some degree.
- Pervert Revenge Mode: Her preferred response to Tomoko's antics.
- Vitriolic Best Buds: The vast majority of her interactions with Tomoko consist of Tomoko saying or doing something insensitive or perverted to her and Yoshida responding with anger and violence. To onlookers, Yoshida appears to be bullying her. Despite this, however, she is shown to genuinely like Tomoko somewhat, and is gradually becoming one of the closest things she has to a friend.
A fairly ordinary girl from Tomoko's class who ends up in her group for their class trip after a falling out with her friend.
- Cloudcuckoolander's Minder: In chapter 106, she prevented Tomoko from saying something to Yoshida that would get her punched. Overall, she has a better grasp on what kind of person Tomoko is than the rest of the school.
- Nice Girl: While she doesn't have a particularly good opinion of Tomoko, she nevertheless treats her with respect and kindness, and even invites Tomoko to eat lunch with her and her friend Mako in chapters 82 and 84 (though it's not clear whether she's doing this out of her own will or only because Ogino asked her to stay in touch with Tomoko during the school trip).
- Noodle Incident: She spends most of the Class Trip thinking about how to make up with her friend Mako, but it's never said what caused the falling out, and they seem to have made up by the end. (A girl who looks like her can be seen in chapter 69 arguing with her friend because the latter accepted an invitation to a group from someone else, which means that the two can't be in the same group during the school trip. That girl is only seen from a distance though, and it's not confirmed whether she's Yuri.)
- Not So Different: Her social life isn't actually that much better than Tomoko's. Both girls are shown to only have one person they consider a true friend (who in both cases is a girl who is more popular and sociable than themselves - Yuu in Tomoko's case, Mako in Yuri's) and aren't shown to be socializing much with other students (though eventually Tomoko and, to a lesser degree, Yoshida become Yuri's acquaintances). Before the second year class trip, when Yuri found out that she can't be in the same group as Mako, she did not join any other group of her own will. The main difference is that Yuri's Only Friend is in the same school and class as Yuri, unlike Yuu.
- Only Sane Woman: She notices how much of an idiot Tomoko is.
- Ordinary High-School Student: Probably the single most ordinary character in the entire series.
Another girl from Tomoko's class who has strange eyes and has similar hair to Yuu. After spending most of her time with her friends in a different group during the class trip, the short time she actually spends with Tomoko turns out to be a disaster for her.
- Ambiguously Gay: She thinks Tomoko is stalking her to sexually harass her, maybe more, which of course frightens her, but when it looks like Tomoko isn't interested in her, Ucchi becomes noticeably miffed.
- In later chapters it starts to look like she might actually have a crush on Tomoko going by her reaction to Tomoko giving her a secret "Thank You" note or how she was able to instantly tell Tomoki was Tomoko's brother just by looking at his face. In chapter 112 she actually leaves Valentine's Day chocolates in Tomoko's locker.
- Aren't You Going to Ravish Me?: Due to Tomoko's mannerisms, comments and actions when interacting with her, she's convinced Tomoko is stalking her, and is obviously creeped out when Tomoko is trying to peek under her skirt. However, when she notes her also peeking under the skirts of other girls, her reaction shows this:"So long as you've got a girl to stare at, you don't care who it is?!"
- She later has the same reaction again when she sees Tomoko going shopping with Yuu who looks similar to herself. Ucchi is convinced that Tomoko is trying to replace her with Yuu.
- Ascended Extra: Made a brief appearance in chapter 59 (as the girl sitting next to Tomoko in a bus and ignoring her to chat with her friends instead) before becoming a recurring character.
- Non-Standard Character Design: Always has Black Bead Eyes. It's so unusual, that even in-universe, Tomoko compared her to an emoji.
- Not What It Looks Like: While she is right in general about Tomoko being a Covert Pervert, she also tends to interpret absolutely everything Tomoko does as her being a perverted stalker, even when Tomoko does something with no ill intent whatsoever.
Tomoki's classmate from middle school, and later also from high school. Revealed to have a crush on Tomoki, much to Kotomi's distress.
- Ascended Extra: She made her first, brief appearances in chapter 25/episode 3 of the anime (as one of the girls who brought Tomoki printouts from school when he was sick) and in chapter 41 (where she was revealed to have a crush on Tomoki). After chapter 83 she becomes a recurring character.
- Cannot Spit It Out: She turns into a Shrinking Violet in Tomoki's presence and is paralyzed by fear of embarrassing herself in front of him, which prevents her from confessing her feelings. It doesn't help that the one time she mustered the courage to try to act on her crush did result in her embarrassing herself in front of Tomoki in chapter 91.
- Imaginary Love Triangle: For a few chapters she was convinced that Tomoko is her romantic rival. Neither Tomoko nor Tomoki had any idea she felt that way.
- In-Series Nickname: After events of chapter 91, Tomoko coins "Dicky-chan" for her.
- Love Hurts: So far her crush on Tomoki has only caused misery and embarrassment for her.
- Mistaken for Index: She has tendency to jump to completely wrong conclusions about people based on little evidence. For instance, in the course of chapter 83 she manages to both mistake Kotomi for Tomoki's sisternote and mistake Tomoko for Tomoki's suitor. In chapter 91, when she finds out that Tomoko is Tomoki's sister she still convinces herself that Tomoko and Kotomi are both Tomoki's sisters.
- Paralyzing Fear of Sexuality: Later chapters show that Akari believes having sexual desires is something that makes one "impure"; as a result, she spends the first chapters after becoming a recurring character insisting that her crush on Tomoki has no sexual element whatsoever. In chapter 101 she finally acknowledges that she is also sexually interested in Tomoki, but this realization makes her loathe herself; in chapter 108 she call both Kotomi and herself "vulgar perverts" in her thoughts.