- Cloud Cuckoolander: Kuroda even notes in his end of volume 1 supplement that, within that volume, she started off as an airhead and over time became simply crazy.
- The Ditz: A big one, but she tends to feel really bad if she messes things up or hurts someone, so no one really says anything.
- Dude Magnet: Run is often shown many times at school surrounded by groups of guys eager to talk to her. The conversations don't tend to last long once Tooru appears.
- Dumb Blonde: Not incredibly stupid or anything, but her mind does not stay focused for more than a second and then there is how accident prone she is.
- Expy: Of Tsukasa.
- Going Commando: Run forgot her panties once.
- Gratuitous English: In episode 3. "No Music No Life" and "Mada (still) No Music Life"
- Heavy Sleeper: To the point that she can do her entire morning routine before waking up.
- Hidden Buxom: Second biggest but only shown when she's not wearing a shirt.
- Insane Troll Logic: One of her many ways of misinterpreting the world.
- Lethal Chef: Assuming she hasn't already killed you preparing the food.
- Nice Girl: Believes the best of everyone and despite being a ditz, she can become devastated if she accidentally hurts someone, or spills something on someone
- Oblivious to Love: She seems to be cheerfully unaware of Tooru's feelings for her, and is the only one in the cast who doesn't find Satou's obsession of her forehead creepy.
- Chapter 73 reveals that Run is confessed to by guys a lot, but she is completely oblivious to their intentions.
- Too Dumb to Live: Her friends literally have to keep her from hurting herself. (But we still love her anyway.)
- The Caretaker: She is very protective of Run.
- Character Development: She initially begins very close to Run and only associating with Nagi and Yuuko because they had a mutual friendship within Run. She also didn't care much for Yutaka's attempts at befriending her. Over time she begins to warm up to both Nagi and Yuuko and invests more in her friendships with Yutaka and Miho. She even starts treating Yuuko better.
- Clingy Jealous Girl: With regard to Run.
- Drowning My Sorrows: Played with. Yuuko comes across Tooru after an argument with Run downing several cans of juice in a similar gesture.
- Dull Eyes of Unhappiness: When Yuuko inadvertently irritates her.
- Hammerspace: When She has her shirt hanging out of her bloomers, it looks like she's just wearing a dress (it goes past her knees), but when it's tucked in...nothing.
- Nonuniform Uniform: Almost always wears a purple cardigan with extra long sleeves over her school uniform. In episode 6 Run convinces her to take it off, and she swaps it for a purple vest.
- Older Than She Looks: Emphasised in episode 5, when she wears swimsuits for elementary schoolers...
- Pet the Dog: She's fond of small animals and children, often giving kids candy. Also she is a great help in the classroom.
- She finds Yutaka annoying, but she's perfectly fine with showing the girl her notes or helping her with problems.
- Yuuko on the other hand...
- School Swimsuit: She's had the same one since elementary school.
- Sitcom Arch-Nemesis: She just doesn't like Yuuko.
- Sweet Tooth: Tooru loves sweets, something that several characters take advantage of when they want to persuade her or win her favor.
- Sugar and Ice Personality: While cold and aloof, as well as sometimes mean, it's shown that she really does like all of her friends, Yuuko included.
- Token Mini-Moe: And she not to happy about it.
- Tsundere: Nagi describes her as this, Run forgets what one is and imagines her with a spear.
- Zettai Ryouiki: Although they tend to slide down since she's so skinny.
- Butt Monkey: Tooru is the main culprit, but nearly everyone constantly makes fun of her/has fun at her expense.
- Catchphrase: She has Nani?note , usually said when she ends up as the Butt Monkey.
- Covert Pervert: At least once:
Yuuko, when handed a hentai manga with a character that resembles her.
Yuuko: I don't like this kind of stuff.
Nagi: You say that, but you're reading the whole thing...
- She also tried to sneak a peek after being told Run had accidentally left home pantieless.
- Expy: She is VERY similar to Mio. Ironically, she is voiced by Minako Kotobuki who voiced Mugi.
- She's got a bit of Mei, too.
- Gag Boobs: She has the biggest pair in the cast only surpassed by Kito. This is often makes her the source of much ire and jokes from Tooru and Nagi.
- Girls Are Really Scared of Horror Movies: Becomes horribly traumatized by just seeing a movie, so much so that she tries to overwrite the memory.
- Godiva Hair: Just barely covering.
- Hartman Hips: A part of her model-like looks.
- Huge Schoolgirl: The tallest of her friends as well as the most developed.
- Kansai Regional Accent: Traces of it in her speech throughout the series (e.g., ending her sentences with "-ya") - her family moved from the Kansai region just before her first year in high school. Also played into her Shrinking Violet role, as she had been worried about people making fun of her accent when she first came - luckily for her the first person she talked to at the entrance exam was Run.
- Marshmallow Hell: She gives one to Tooru by accident once. Tooru passed out from lack of oxygen.
- Nice Girl: She's amongst the nicest person in the cast, often tagging along with Run and Nagi's quirks and it's only because of her forgiving personality that most of Tooru's actions towards her are Played for Laughs.
- Rapunzel Hair: It comes down to her hips.
- Shrinking Violet: Played with, she can be very shy when meeting new people, but can be very open with her friends.
- Yamato Nadeshiko: When asked what she wants to be in the future she cheerfully responds to being a wife.
Nagisa "Nagi" Tennōji
- Amazingly Embarrassing Parents: Her father is this, much to her annoyance, shedding tears about how beautiful she's gotten and meeting her teachers for Parent-Teacher conferences decides to instead spend the entire time talking about how cute she is.
- Between My Legs: In episode 2.
- Blind Without 'Em: Her sight is so bad without her glasses she'll often mistake mannequins for actual people.
- Brainy Brunette: She is a book worm and when one of the girls is struggling with a question its her they will go to.
- Beautiful All Along: When she takes off the glasses and lets loose her hair, she rivals Yuuko in model worthy looks.
- Expy: Of Azumanga Daioh's Yomi.
- Girlish Pigtails: Like her glasses she uses them to dull her looks.
- Hachimaki: She wears one when preparing for her New Years diet.
- Meganekko: Ironically, she has no problem wearing contacts, but because her dad freaks out she prefers glasses.
- Nonuniform Uniform: Usually wears a beige cardigan over her school uniform, except during the summer. Instead she has it tied around her waist.
- Not So Above It All: Despite reprimanding Run for her childish behavior she's often joins in said behavior so she doesn't feel left out.
- Otaku: A good majority of her knowledge about life, like love, comes from manga she's read. She also calls a stack of about twenty manga small.
- Ojou Ringlets: During the Festival Episode.
- Serious Business: She takes the Ibod very seriously.
- Straight Man: She's often this to the many quirky personalities around her, especially to Run.
- Weight Woe: She often worries about her weight despite maintaining a very lithe figure.
Voiced by: Ai Matayoshi (JP)
- Book Dumb: She often scores low grades on her exams and looks to Miho and Tooru to tutor her. Her behavior of sleeping in classes and slacking off in her schoolwork doesn't help her situation either.
- Eyes Always Shut: Most of the time.
- Hidden Buxom: In a similar vein as Run, Yutaka sports an impressive bust amongst her peers when she's not wearing loose clothing.
- Third-Person Person: Though the subs don't show it, at first.
- Control Freak: She's known for her overbearing and controlling attitude towards Yutaka. This attitude was strong even back in middle school as her nickname then was "Remote Control".
- Straight Man: To Yutaka.
- Wrestler in All of Us: One of her many ways of disciplining Yutaka is to subdue her with a number of wrestling moves.
- Apathetic Teacher: She does the bare minimum amount of work, and her reaction to any disturbances is pretty much to shrug and go "whatever".
- Older Than She Looks: Kito and Sato find a picture of her wearing a sailor uniform and assume she's cosplaying. Until they see that the picture is dated over ten years ago.
- Shipper on Deck: She likes to ship Kito and Satou when she sees them argue.
- Why Does It Have To Be Cats?: When a cat decides to find it's way inside the school she largely avoids it and gets scared stiff when making contact with it.
- Gag Boobs: When happening to come across her scattered laundry by mistake both Tooru and Nagi wonder if her bra was some kind of melon holder.
- Hot-Blooded: She tends to make people, namely her students, uncomfortable with her eccentric personality and loud voice.
- Irony: She urges all of her students to come to her with their problems and tries to inspire the best in them but her actions tend to push them away compared to Kamade who doesn't bother to influence them and tells her students not to stress about the future and wins their admiration.
- No Inside Voice: In school she is always shown energetically shouting at her students and encouraging them in their schoolwork.
- Sitcom Archnemesis: With Sato. She dislikes his childish demeanor and lack of effort he puts in his job. He in turn dislikes
- Fetish: Run's forehead.
- Hot for Teacher: In spite of his quirks, his Bishōnen looks has won the affection of many of the female student body.
- Ill Guy: He's very sickly and often takes medicine to remedy his illnesses but it's Played for Laughs at times to play up his unusual personality.
- Big Sister Worship: She thinks very highly of her sister and when her classmates ask her how her sister is like she gives them a long list of traits she's exceptional in.
- The Caretaker: Similarly like Tooru she is very protective of Yuuko.
- Clingy Jealous Girl: She's very jealous of Tooru from the praises her sister gives her when she's not around.
- Foolish Sibling, Responsible Sibling: She's the responsible to Yuuko's foolish. She's very confident and capable in her schoolwork and often reprimands Yuuko when she doesn't do things properly.