- Voiced by: Jun Fukuyama
The main character who ends up becoming the new leader of the Fourth Guard Squad.
- Accidental Pervert: On two occasions in the first episode alone, both times on Haruka. Aoi immediately calls him out on the first one when a gust of wind blows up Haruka's skirt, and the second one is after he accidentally gets a Panty Shot of her while searching for a dog in a train.
- Balanced Harem: In the anime, none of the girls interested in Naoto has a significant lead over the others, mostly because he's Oblivious to Love and doesn't notice anyway. Noa however, states in episode 8 that she doesn't mind a little competition.
- Bridal Carry: He carried Aoi out of a train in this manner at the end of episode 11.
- Cassandra Truth: He attempts to explain Haruka's nakedness in episode 6 as her losing her clothing to throw off assassin cats. It doesn't sound very believeable to Aoi, despite the fact that she saw cats around Haruka's clothing.
- Clueless Chick Magnet: He never seems to notice the affection girls feel for him. Haruka, Aoi, and Bernina all seem to be interested in him in the original light novel, and the anime adds in Mari and Noa.
- Treads dangerous territory at the end of episode 7 when Aoi, Haruka, and Noa all confront him in the church, thanks to Iida's meddling.
- Credits Running Sequence: He does one in the ending credits.
- Cursed with Awesome: He is rather disappointed in the fact, that he'll never become a train driver because of his involvement in stopping various crimes throughout the station.
- Forgotten First Meeting: After saving Haruka when she falls off a ladder in the first episode, she quietly comments that it's the second time he's saved her, indicating that he's done it before and forgot about it. Episode 6 reveals their first interaction in a Flash Back, and is almost a repeat of what happened when they first met, with Haruka being trapped inside a closet, but Naoto telling her he called for help. Later he tells her not to hate the railway because of this, and says it to her again when he locks her in to prevent the thieves from getting to her.
- Info Dump: He does them in the next episode preview credits, spouting off some information about trains or train stations, before being interrupted by one of the girls who then tells viewers what the next episode is really about.
- Non-Action Guy: Played straight for the most part. Though he seems capable in a fight, as seen in episode 3, most of the time he lets Aoi and Shou do the fighting, such as when protecting Bernina aboard a train in episodes 10 and 11. Justified however, in that while he is part of railway security, he's much more interested in becoming an engineer.
- Oblivious to Love: He doesn't seem to realize that many of the show's women are falling for him.
- Rail Enthusiast: He goes into spurs at the previews for the next episode, showcasing the history and details of specific trains in Japanese history, with another character coming in and telling him to stop talking and go back to the actual preview.
- Secret Keeper: He is asked to keep one in episode 10, after finding out Bernina is actually a girl.
- Straight Man: He's showing shades of one, especially compared to Aoi.
- Sustained Misunderstanding: He receives what he believes is a death threat letter in episode 6 and shows it to Haruka, who believes he may be a target for an assassination due to his role in foiling various plots against the JNR. Aoi dropping her phone while calling them convinces them he is being targeted, and various other things happen to sustain said misunderstanding, such as getting shot at (by an airsoft gun that Aoi had on her), and later being targeted by some thieves who broke into the train museum. At the end, Naoto shows the letter to Aoi, who then figures out it's just an advertisement for life insurance. When she ridicules him for it, he mentions getting shot at. But Aoi, who accidentally shot at him, plays dumb, and acts like he was just overreacting.
- Unwanted Harem: In the anime, Naoto gradually gains one as the show progresses. Though it's somewhat subtle at first, by episode 7 almost every female character is interested in him, and start showing their feelings more towards him. Unfortunately he's still Oblivious to Love, which upsets them more. And episode 10 introduces another one...
Aoi: You're a lucky guy for being surrounded by cute girls, Takayama.Naoto: Are you one of them, Sakurai?
- Gets lampshaded by Aoi in episode 7, complete with Naoto's retort:
- Wham Line: He accidentally gives one to Aoi in episode 10, when she says she doesn't want to rely on a guy for support like in Cinderella. He then mentions that any guy who hits on her is going to have a rough time. His statement shocks her so much she is unable to reply.
- Voiced by: Manami Numakura
The heroine and a member of the Fourth Guard Squad.
- Action Girl: It's how she was introduced.
- Almost Kiss: Happens between Aoi and Naoto at the end of episode 9 after he says she looks cute in dresses, prompting her to turn around really close to him.
- Artistic License Gun Safety: In episode 6, Aoi pulls out a gun and aims it at Naoto, thinking he was up to no good with Haruka. Though she probably didn't really mean to fire, a person in a penguin suit runs into her, and accidentally causes her to fire at them. Though it was just an airsoft gun, the shot fired from it hits a small statue near the two, causing them to think a sniper was firing at them. Made more of a Face Palm situation by the fact that Aoi was raised by a police officer, and should know better than to aim a gun, even an airsoft one, at someone if she wasn't intending to shoot them.
- The Big Girl
- Blood Knight: She seems to enjoy the chasing down, fighting, and apprehending criminals aspect of her job quite a lot, even though it's technically a secondary function of it. Naoto constantly reminds her that passenger safety is their top priority. Aoi claims it's due to her father's influence on her since he was a police officer and wanted her to become one as well.
- Bridal Carry: fills the bridal part of it at the end of episode 11.
- Clingy Jealous Girl: Starts showing signs of this in episode 7, when Mari is seen working at the same restaurant near the training academy they're at, and Haruka pulls up close to his seat. She makes a Deadpan Snarker comment to him about being surrounded by girls, then "accidentally" spills her drink in his general direction. Then after Mari gives him a different side dish than every one else because he says he doesn't like leeks, Aoi reaches over and eats it while Haruka thinks to herself that Mari knows quite a bit about him.
- Date Peepers: Though technically not on a date, Aoi follows Haruka and Naoto around in episode 6 after seeing them together. Especially after seeing them run off while holding hands as if getting intimate.
- Does Not Like Men: Aoi appears to be this way at first, and constantly accuses Naoto of being a pervert.
- Double Standard: Abuse, Female on Male: Aoi sometimes hits Naoto, even if he was innocent, such as in episode 5 after they're done chasing after a bomber suspect.
- In episode 6 she points a gun at him. And fires. Luckily she misses and destroys a small figurine nearby.
- Dynamic Entry: Aoi does one at the end of episode 10, kneeing a bad guy in the face as he attempts to attack Naoto and Bernina.
- False Start: Aoi nearly gives one to Naoto near the end of episode 11 when they're both stuck in a runaway train. They are interrupted by Captain Gonou who catches up to them in her security train to help stop their runaway car.
- The Gunslinger: Not only Aoi is very athletic, she's a good shot with a handgun (on one hand) as well.
- Kick Chick: Aoi uses her legs a lot in fights.
- Love Epiphany: Though it's hinted at earlier, Aoi definitely starts realizing her feelings for Naoto in episode 5, especially after he finds her when they get separated near the end of the episode.
- Major Injury Underreaction: She just manages to avoid getting blown to smithereens in episode 5 after a suspect she's chasing with Naoto throws his bomb onto the track while they're pursuing him. Though she's bleeding from her arm, and seems to be suffering a concussion as well, she tells Naoto to stand in front of her so she can shoot at a safety wire rigged to warn train engineers of fallen rocks on the tracks to stop it from driving over the section the bomber blew up.
- Miss Fanservice: She's usually shown rather suggestively, and has her jacket unbuttoned compared to Haruka who has hers buttoned up. Episode 5 also does this extensively, with very suggestive shots and camera angles on her in her uniform.
- No Sense of Personal Space: Despite saying she hates men, Aoi tends to get rather up close and personal to Naoto several times throughout the show.
- She's Got Legs: Aoi's legs are prominently displayed in her uniform, especially since she tends to make liberal use of her feet in a fight.
- Tomboy and Girly Girl: Aoi is markedly more tomboy compared to Haruka.
- Tsundere: Aoi gradually develops this way towards Naoto. She doesn't like him at first, but gradually develops feelings for him and acts hot and cold towards him.
- Unprovoked Pervert Payback: Naoto gets punched in the face by Aoi in episode 6 after she assumes that he was a perverted lech for stripping Haruka down to nakedness.
- Violently Protective Girlfriend: Invokes this in episode 4 after Naoto gets stabbed by a crazed man. She screams his name, rushes the crazed man, kicks his knife away (which also has no sign of blood on it), and then slams the perpetrator on the ground to subdue him.
- What the Hell, Hero??: She gets incredibly upset at Naoto in episode 7 when he says he wants to be an engineer instead of a security officer like her. She acts rather cold and distant towards him for much of the rest of the episode and sabotages their training session.
- Voiced by: Maaya Uchida
The other heroine and a member of the Fourth Guard Squad.
- Beware the Nice Ones: One of the purse-snatching thugs from the first episode gets an AEDnote thrown at his face when he tries to attack her.
- Clingy Jealous Girl: Gets angry at Naoto at the end of episode 7 after thinking he was ditching their group to secretly meet up with Aoi. Then during episode 8, after Noa latches onto his arm inside the church, she stands up with an angry look. However, the latter shoots her a Death Glare, which immediately causes her to sit back down.
- Clothing Damage: She suffers a tear in her school uniform in episode 6, and also gradually sheds her clothing throughout the episode due to running away with Naoto from a possible threat on his life.
- Cry Cute: At the end of episode 7, she thinks Naoto lied to her to secretly meet up with Aoi at an empty church.
- Damsel in Distress: Happens to her in episode 11.
- False Start: Haruka seems nearly give a Love Confession to Naoto a couple of times in episode 6, but it's interrupted each time by outside forces, such as a couple of thieves, and later Aoi.
- The Glomp:
- She does this to Naoto in episode 6, while naked, after the two thieves chasing them are subdued by Aoi, Iida, and Hitomi.
- She does it again in episode 11 after he and Aoi are saved when they fail to escape the runaway train in time earlier.
- Hopeless Suitor: Though she doesn't specifically say anything about it, after Naoto mentions waiting for Aoi to do a patrol with, Haruka definitely has a look on her face suggesting that she's losing ground with him to her, especially after she walks away from him. However, episode 6 spends a lot of time with her and Naoto.
- Innocent Fanservice Girl: Haruka in episode 6. She gradually takes off her clothing after cats chase after them due to the catnip they fell on earlier, until she's completely naked by the end. Despite that, she doesn't seem embarrassed that Naoto sees her in the nude, though it may also be because he's constantly being harassed by Aoi by that point.
- Love Hurts: Haruka always seems a bit upset anytime Naoto is spending too much time with another girl, especially Aoi.
- Miss Fanservice: With her big Gainaxing breasts. She has also few Panty Shot scenes and appears naked also.
- Marilyn Maneuver: Happen to Haruka in the first episode because of the wind. Another episode has Aoi victim in the same way. Both times strangely without glimpse of panties despite to be a fanservice show.
- Marshmallow Hell: An episode has Haruka use this to calm down a lost kid.
- Moment Killer: During moments when Haruka seems to be getting closer to Naoto, something tends to inadvertently interrupt them, usually Aoi.
- Patient Childhood Love Interest: Played straight with Haruka. Though she's only had a brief encounter with him, she still remembers him and isn't being overly aggressive in displaying her affections towards him, though she doesn't like it when other girls do so, such as Noa.
- Super-Speed Reading: Haruka shows this in episode 3 while looking at reports of the previous day when Mari mentions her friend possibly having been kidnapped. She does it again in episode 8, memorizing a large dictionary-sized manual for how to operate the little train car the group is using to deliver a human organ to a hospital in time.
- Tomboy and Girly Girl: Aoi is markedly more tomboy compared to her.
- Up to Eleven: Apparently, Haruka memorized the time tables of the train system. This allows her to calculate the fastest time to get to multiple places across the Japanese railway system (such as during the purse snatchers incident in Episode 1, where instead of using the railways, they use the maintenance train instead to catch up).
- Voiced by: Satoshi Hino
A member of the Fourth Guard Squad.
- Big Eater: Seen on tv at an eating contest in episode 6. The announcer mentions that he ate quite a large amount of food in the preliminary round. And in episode 7, he's constantly complaining about being hungry and wondering when the next meal is.
- The Big Guy
- Food as Bribe: Goes to the training center in episode 7 when he hears that the food at a nearby station is good.
- Mundane Made Awesome: Shou while attempting to pedal on the bike in episode 8. Later he and Aoi scream while attempting to counterbalance the train car from tipping over during curved sections of the track. Naoto tells them that they sound silly when they do it.
- Voiced by: Yui Horie
The original leader of the Fourth Guard Squad.
- Ambiguously Gay: She's this for Hitomi, her friend and the instructor.
- Heterosexual Life-Partners: With Hitomi.
- Reasonable Authority Figure: For the main character's team. She gives them a surprising amount of freedom to perform their missions however they see fit, such as when they defuse a bomb in episode 2, or when they stop a crazed man from attacking Noa in episode 4.
- The Show Must Go On: She does this in episode 4, when a crazed man shows up on stage to attack Noa during her concert. She makes it seem like it's part of the act, and has Naoto protect Noa. Because of the way Iida portrayed the situation, the audience is none the wiser that said attacker really was intent on harming Noa were it not for Naoto and the others protecting her, and a crowd panic scenario is avoided.
- Voiced by: Mai Nakahara
The instructor for Tokyo Security Force.
- Heterosexual Life-Partners: With Iida.
- Scary Shiny Glasses: Hitomi has this look on her during the opening. Then shortly after Iida hugs her, the glasses revert to normal and her eyes are visible.
- Voiced by: Hiromi Igarashi
A classmate of Naoto's.
- Patient Childhood Love Interest: Potentially played straight with Mari in the anime. She definitely spent time with Naoto growing up, and knows a lot of little details about him, such as his favorite side dishes. Like Haruka, she hasn't made any overt romantic moves towards him, though the other girls certainly sense the connection she has with him. However in episode 9 she mentions Noa as a rival, and says it's a secret when Haruka inquires about it.
- Promoted to Love Interest: In the original light novels, she's moderately close at best with Naoto and seemingly develops an interest in Shou after he rescues her. In the anime, she seems to have become a Patient Childhood Love Interest for Naoto, and seems to know everything about him.
- Voiced by: Minori Chihara
The main vocal of the idol unit unoB.
- Bodyguard Crush: She seems interested in Naoto after he saves her life from a crazed man in episode 4 of the anime.
- Death Glare: Does one to Haruka in episode 8 when the latter stood up after being uncomfortable watching the former latching herself around Naoto's arm. This causes Haruka to meekly sit back down.
- The Determinator: She's determined to go through with her concert in episode 4 after someone sends her a death threat and replaces her confetti with flash paper during a rehearsal as a warning to her. However, she feels that she has come to far to back down and cancel in her career. And fortunately for her, the main characters are assigned to protect her.
- Miss Fanservice: Being an idol, she also gets this treatment in episode 4.
- Promoted to Love Interest: She doesn't really show any interest in him in the light novel, but displays some very forward affection for him in the anime; the fanbook also has her showing some signs of attraction towards him.
- Voiced by: Hiromi Konno
Fifth-in-line for the throne of the small country Atela.