Principal Takako Tsuboi
- Butt-Monkey: Nothing goes her way ever since Sousuke enrolls in JH. Bombs go off in the shoe lockers, her personal car gets stripped down, up to the chassis, to search for potential explosives. Sousuke's EMP fries her laptop to do her work. A biological weapon goes off in her classroom... Needless to say, most of her headaches involves not only him, but whatever things he brings to school.
- Reasonable Authority Figure: Highly averted with Sousuke whenever he does something like using his military gear in a class or school event.
- Taking the Bullet: Tried to stand up to Gauron when he kidnaps Kaname, but has a slight Heroic BSoD when he threatens to put a bullet in her forehead.
The art teacher of 2-4. Known to be a Cloudcuckoolander in explaining his passion for his work to the student body.
- Cloudcuckoolander: Tends to talk with long speeches that at one point, Ms. Kagurazaka needs to stop him.
The PE teacher. He sees Sousuke and Atsunobu as good for nothing students.
- Sitcom Arch-Nemesis: To Sousuke and Atsonobu after the latter decided that the student council will be responsible for selling bread to student during morning breaks.
The old janitor of Jindai High.
- Almighty Janitor: Just read the rest of his tropes below and you'll know why.
- Cool Old Guy: Despite his advanced age, he still manages to fight (and scare the crap out of) both Sousuke and Issei.
- Berserk Button: DO NOT harm his pet koi Catherine. Sousuke and Issei learn this the hard way after they make the mistake of catching, cooking and serving the aforementioned pet koi to Mr. Ohnuki.
- Beware the Nice Ones: Generally patient with Sousuke and Issei's inability to get along and work together... until they feed him his pet koi.
- Chainsaw Good: His Weapon of Choice is a chainsaw.
- Nigh Invulnerable: When enraged enough. To quote Sousuke, "Live ammo has no effect..." He even chews on a grenade!
- Slasher Smile: Displays this as he fights both Sousuke and Issei.
The unnamed nurse in the school.
The mysterious president of the Jindai High's Student Council and a third year student. He is highly intelligent and seems to be able to deal with any situation - no matter how difficult. His behavior is always calm and he is never seen angry. He often considers Sousuke's behavior a reasonable response to the kind of situations he finds himself in, much to the frustration of Kaname. He assigns Sousuke to be the head of security in the Student Council. He and Sousuke share a mutual respect.
- Big Brother Is Watching: He is the sole source of information whenever Sousuke mentions someone's weakness(es).
- Dissonant Serenity: He allows Sousuke's antics as long as it is reasonable, and even whenever they aren't, he rarely shows more than a sternly admonishing look. Lampshaded by himself, as he tells Sousuke that after he graduates, the next SC president may even call him out on it.
- The Comically Serious: On par with Sousuke, although being much more expressive (he smiles often, something Sousuke cannot boast of) and sometimes becoming trollingly serious.
- Knew It All Along: In the events of Continuing On My Own, Atsunobu tells Sousuke that he rightly suspects that Kaname is sought after by various bad guys due to her hidden knowledge and also suspects that Sosuke is really working for an armed covert group (Mithril), but chooses not to pry further.
- Limited Wardrobe: Always wear his white school uniform, even in the Beach Episode.
- Manipulative Bastard: Well, only towards Kaname, and nothing ever malevolent.
- Reasonable Authority Figure: He is incredibly calm and professional, as well as a good president overall. He sometimes even agrees with Sousuke's antics, which grants him the latter's admiration. In one episode of Fumoffu, Sousuke blows up his shoe locker after finding an unknown letter inside, and while it caused lots of property destruction, Hayashimuzu shockingly considered Sousuke's actions okay and reasonable under the circumstances.
- Secret Secret-Keeper: He is revealed to have deduced about Kaname and Mithril a long time ago, which comes as a surprise (for Kaname and Sousuke, at least).
- The Stoic: Always keep the same look under any circumstances.
- Stoic Spectacles: Extension of the above two.
- Student Council President: And is scarily efficient at manipulating Kaname to do his bidding.
- Younger Than He Looks: His white hair, frame and general style can make incredibly easy to forget that he is a high-schooler.
Ren Mikihara is the Secretary of Jindai High's Student Council, friend of Kaname's. Beautiful and dependable; she seems to have feelings for Atsunobu Hayashimizu, the Student Council's president. However, much about her is still unknown. Kaname prefers to address her as Oren-san due to her Ojou looks and extremely formal speech pattern.
- Big Fancy House: Her house is a traditional Japanese mansion, fitting as it also function as Yakuza headquarter. Come with a requisite The Thing That Goes "Doink!".
- Curtains Match the Window: She has purple eyes and purple hair.
- Face Death with Dignity: Despite the trope being lampshaded when the class are Trapped in Containment in Fumoffu, she's the only one who remains calm and dignified.
- The Ingenue: She once walked into a red-light district and was approached by many people with....not good intention and didn't seem to mind them a lot. Kaname, who was listening to story, was not amused.Kaname: Oh, for the love of.. Uhm, Oren? A girl like you really shouldn't go into those kind of place alone, you hear me?!Ren: Uhm, huh?
- Katanas Are Just Better: She doesn't use them but certainly thinks so. That probably has to do with her affiliation with the Yakuza.
- Keigo: Her style of speech which she uses even to her classmates.
- Nice Girl: Ren's very nice to people, even to Sousuke
- Subordinate Excuse: It' implied she has feelings for Hayashimuzu, and this is the reason she's the secretary of the Student Council.
- Team Mom
- Tomboy and Girly Girl: Has this dynamic with Kaname as the Girly Girl.
- Yakuza Princess: She's the daughter of a Yakuza boss, as revealed in ep 10 of Fumoffu.
- Yamato Nadeshiko: A tea-serving, katana-loving, dependable Japanese lady.
- You Gotta Have Blue Hair: She has purple hair.
Kaname's humble best friend who is usually seen carrying around her trusty camera. She is constantly trying to bring Chidori and Sagara together, however impossible it may seem given Sagara's tendency to blow things up at whim. However, in the novel 'Continuing On My Own', she was held hostage by Amalgam's agents as bait to lure Sousuke so they could kill him and find Kaname. Kyoko was seriously injured during the rescue attempt and is currently still recovering in the hospital after being rescued by Wraith.
- Camera Fiend: She always has her camera with her.
Sosuke's Arm Slave loving classmate. He shares the same amount of passion to AS as Sousuke and could be considered Sousuke's best school friend besides Kaname. His father is Shintaro Kazama and a secretary of Narashino's Assault Machine Troop. Shinji's love for AS began when his dad failed to become an AS pilot. As a result of his father's failure, Shinji strives to discover the result of the failure and to fulfill his father's dream of becoming a pilot. There is no indication as to what happened to his mother, but it's assumed that Shintaro is a widower before the series started.
- Birds of a Feather: He bonds with Sousuke through their shared love of Arm Slaves.
- Expy: He's a nerdy kid, obsessed with the military the protagonist works for, and strives to be a mecha pilot. Is he related to Kensuke Aida? (Bonus points for being named Shinji.)
- Otaku: He's a straight-up version of the trope, specifically a military AS fan.
- "Well Done, Dad!" Guy: His father is this, as he is unable to pilot an AS and is simply support staff. After being slapped by Sousuke, Shinji comes around and eventually joins his father in an (non-combat) AS.
- Idiot Houdini: Sosuke is partially at fault for bringing his wares to school in the first place, yet he is the only one to blame whenever Onodera activates the wares.
- In-Series Nickname: His friends usually call him Ono-D.
- What Does This Button Do?: His running gag and he never learns any better not to touch Sosuke's wares.
- Ship Tease: He and Kyoko have attraction for each other.
First appears as Woman Scorned to Kaname because her ex-boyfriend fell in love with Kaname and broke up with her. She then asked Sosuke to be her fake boyfriend in front of her friends. She becomes Kaname's friend and joins the regular school character casts.
The leader of Jindai High School's Karate club, which he is very skilled at. However, he is extremely nearsighted and can see clearly only when wearing his glasses, which leads to several comical incidents. His sense of pride cannot accept the fact that he was defeated by Sousuke, and he is constantly challenging him to rematches - which Sousuke usually avoids - intentionally or not. He also has a huge crush on Kaname.
- Anguished Declaration of Love: He accidentally gives one to Sousuke (instead of Kaname) during a novel side story. Extra Irony points in that, for every single one of the other love confessions Sousuke had received, he had either misunderstood them or blown them off. But for this one, Sousuke happened to vaguely understand its implications, and ended up getting weirded out by it, acting shocked that Tsubaki would be "that kind of person."
- Arrogant Kung-Fu Guy: He's a more comical (and less evil) example; his extreme nearsightedness prevents him from being taken seriously. Think of Mousse and you'll have an approximate dimension.
- Back-to-Back Badasses: An episode of Fumoffu shows how they manage to do this when they're forced to team up. Unfortunately, it still doesn't work considering who they're up against.
- Battle Aura: Putting on his glasses improves his combat efficiency so much that he manifests one of these.
- Big Ol' Eyebrows: Has the biggest eyebrows out of all the characters in the series, after Gauron anyway.
- Blind Without 'Em: Sort of. He's actually reasonably functional without his Nerd Glasses, but his poor vision and his reluctance to wear his glasses does result in regular bouts of mistaken identity comedy (see above).
- He-Man Woman Hater: He firmly believes that women should Stay in the Kitchen and acts very condescending towards his female peers, except Kaname, who, he's developed a crush on. However, he still patronized her when they met again after their first meeting, only changed his attitude when he put his glasses on and recognize her.
- Martial Arts Headband: Issei always wear a white headband while even in school.
- Maybe Ever After: With Mizuki Inaba. She wants to, he is not interested. See No Guy Wants to Be Chased below.
- Mistaken for Gay: In the novel's side story, where he accidentally confesses to Sousuke instead of Kaname (due to his glasses being off), while he was trying to reveal to Mizuki that he won't reciprocate her feelings because of this person he loves. Sousuke is shown to become very disgusted and nervous after receiving this confession, and afterwards, the entire school thinks he has a gay crush on Sousuke.
- Nerd Glasses: What he wears to compensate his poor eyesight.
- No Guy Wants to Be Chased: Mizuki Inaba fell in love with him but he doesn't appreciate her aggressive tactics.
- Pet the Dog: Despite his rivalry with Sousuke, he doesn't join in the students mockery when Sousuke loses the bet and is forced to strip off.
- Rivals Team Up: After an entire episode in Fumoffu dedicated to the Janitor trying to get him to work in harmony with Sousuke... this ends up happening after Sousuke catches the Janitor's pet koi (which he thought of as his daughter) and they both cooked it and fed it to the Janitor. Who promptly went Ax-Crazy with a chainsaw and scared the crap out of them. They end up working in harmony to fend off the guy's attacks... except even then, they still end up getting overwhelmed.
- Testosterone Poisoning: He's one of the few people who can get on Sousuke's nerves. As a result violence often ensues whenever they're in the same room.
One of two members of the Social Sciences Club. He gets into a contest with Hiromi and Sousuke to see who can pick up the most girls in a bid to get the last vacant clubroom.
A junior student, she's the one who wrote a love letter to Sousuke, which was blown to shreds in a controlled explosion since he treated it as if an IED was planted at the shoe locker. Ena is also the head of the Drama Club and works part-time at the Club C&J, which began rumors that she was in the enjo kosai business.
- All Love Is Unrequited: Her love letter gets taken out by Sousuke. As such, she gets no response if Sousuke like hers.
Mizuki's ex-boyfriend who ended their relationship in order to pursue Kaname.
- Small Role, Big Impact: Satoru's role in ending his relationship with Mizuki enabled her to look for someone else.