Attack of the 50-Foot Whatever: In Episode 11 after drinking a health drink that was only meant for mermaids. The affair makes him Genre Savvy because he never trusts a mermaid drink (or drink offered by a mermaid) again.
Badass Normal: He's a normal human that lives with superpowered mermaids. Most of them try (and fail) to kill him.
Spider-Sense: By the fifth episode, he's dodging Maki's attacks in his sleep. He can also use it to detect whe someone's about to break The Masquerade.
Suplex Finisher: He does this to Shark Fujishiro when he is attacked during the festival.
The Power of Love: In the anime's finale his voice reached Sun despite her being drugged and immediately afterward he activated the Super Mode without Sun's Song to power him up. "I don't need it. Just being near you fills me with unlimited power!"
Took a Level in Badass: Pretty weak in most episodes but steps up in the anime's finale. In Chapter 60 of the manga he reveals being chased and beaten up by Sun's father has made him superhumanly fast, agile, and durable.
Took a Level in Jerkass: In Episode 25 he was uncharacteristically douchey towards Sun, though he got better after realizing she was in danger.
Too Kinky to Torture: When Luna tries to punish him by tying him up and repeatedly jamming her heel into his crotch from behind, he enjoys it.
Unwanted Harem: Sun, her Mom (though she's more of a Shipper on Deck for her daughter that's having fun at his expense), Lunar, Mawari, and Class Rep. In the manga Saru's little sister Satori, Maki, Maki's little sister Fuki, and Sun's childhood friend Maruko join in on it as well.
First Girl Wins: First girl introduced and the one Nagasumi stays devoted to.
Gainaxing: During Sun's contest against Luna in the anime, she jiggles quite a bit. In the manga's pool chapter this is the reason all the boys are staring at her and Akeno.
High-Pressure Emotion: After trying different poses in front of a mirror with a pair of cat ears, her face heats up like a steam boiler due to embarrassment.
Instant Fan Club: Latent until Lunar showed up. Then suddenly she had her own militant faction that was willing to kill her fiancÚ for more of her attention.
Madness Mantra: When every other mermaid character (except Jupiter) and Saru's little sister announce they are in love with Nagasumi, Sun begins chanting "I have faith in Nagasumi..." in a Creepy Monotone until she collapses from stress.
Mafia Princess: Yakuza princess in this case. Her family operates in the Seto region.
Song Of Courage: One of her songs is the "Song of Heroes' which can empower Nagasumi. In the manga she also uses it on her father when he's fighting Luna's Papa.
Speak Now or Forever Hold Your Peace: Sun crashes Nagasumi's wedding to Lunar dressed in a white kimono, sarashi, and carrying a katana, and announces her intent to take back her fiancÚ by force, even if it means renouncing her family ties and declaring war on the Edomae syndicate.
Baleful Polymorph: Is temporarily transformed into a mermaid after accidentally using a magic seashell meant for Nagasumi. The others pass it off as a dream once she reverts to being human, but the narration hints she kept quiet after realizing what she'd seen was supposed to be a secret.
The Beast Master: She can summon a horde of cats with a whistle. These are beasts in the eyes of merfolk. It's downplayed because even though she can summon them, she can't control them.
Saru: I had no idea Mawari had gotten so good at controlling caaatttssss!
Catchphrase: "Must Mawari teach you the rules of this society?"
Control Freak: She's called the "Demonic" head of the Disipline Comittee for a reason.
Covert Pervert: Was a bit too enthusiastic about checking out the Class Rep's three sizes in the bathhouse, and told Nagasumi she was disappointed she hadn't been able to grope Sun as well in the anime. That said, she does not think Girl on Girl Is Hot.
Genki Girl: She pursues her "Sense of Justice" with great energy!
Lawful Stupid: Played for laughs. Due to her desire to be a "good cop", she tries to be Lawful Good, but due to her overzealousness, she veers towards this instead.
Secret Secret Keeper: It's strongly implied she knows the truth about Sun and the merfolk world, but chooses to keep quiet about it.
Sympathetic Inspector Antagonist: Friends with the other characters, but summoning cats, when the mermaids are terrified of them, makes her an antagonist sometimes. She's not an actual police official, because she's too young, but plans to become one when she grows up.
Love Epiphany: At first Lunar was going to marry Nagasumi solely because she was "stealing" him away from Sun, but after Nagasumi gives a passionate speech to her dad she seems to genuinely fall for him.
Magic Music: Her favorite is the "Song of War", which turns its audience into mindless warriors. She learned it from her mother as a lullaby.
Missing Mom: According to her father, Lunar's mom ran away from her family. Chapter 66 reveals, 10 years prior, Lunar's mom got sentenced to prison for attempting to run over Lunar Papa (among other charges) for being more attentive to the company than his family. She was offered a completely waived sentence but refused out of spite. In the process, she also divorced him.
Mistaken for Gay: Saturn hates Lunar just as much as she hates Nagasumi because she believes Lunar wants Sun.
Mistress and Servant Boy: She tries to force Nagasumi into one of these relationships. She inists on calling him 'manservant' rather than his given name.
Vitriolic Best Buds: More obvious in the manga, but for all her claims of hate it eventually becomes clear that Sun is very important to Lunar.
Yandere: How much it was for Nagasumi's love and how much was to one-up Sun is open for debate but she certainly had extreme measures.
Tsundere: Mellows in the second half of the series into this, for both Nagasumi and Sun. For the former, she'll openly flirt with but violently deny actually liking him. For the latter we have this gem:
—''We rearranged our schedule to see you, but don't get the wrong idea! It's not because we wanted to have fun with you!"
Cool Sword: One with a long history, but he doesn't get to use it until the anime's climax.
Hikikomori: After a traumatic experience in a vast desert when he was young, he has developed a severe case of agoraphobia and never truly went outdoors until transferring to Nagasumi's class. The term is mentioned in his joint Image Song with Saru.
Lonely Rich Kid: He's in love with Sun because she didn't care about money or status. That and she played a weird version of house with him.
Rich Bastard: He uses money to solve his problems. Sun calls him out on this in his debut episode and he gets a little better about it.
Mistaken for Dying: In Episode 24 everyone thinks he's terminally ill, and it gets to the point where Mikawa himself thinks he's dying..
All Amazons Want Hercules: Implied to prefer men who can defeat her in combat via a hallucination-inducing love potion Nagasumi uses. Under the influence, she sees Nagasumi as a martial artist, then proceeds to take her hairband off, coyly says that since she's lost to him, he can do anything to her.
Anti-Villain: Type 5. While she is a antagonist to the main pair, if she didn't do her job there would be more problems for everyone.
Big Brother Worship: Adored her older brother as a child and wants to be like him... but hates him for disgracing their family with his disappearance and one of her secondary missions is to execute him if she finds him.
Buxom Is Better: According to Saru, Akeno is even bustier than Sun, and she become the centre of attention in Episode 17 for this reason. Even Mawari, Gozaburo, and Fujishiro think she's "vexingly sexy".
Phrase Catcher: She's referred to multiple times as 'vexingly sexy' for an episode.
Even the Girls Want Her: Mawari and a few other girls in the class call her "vexingly sexy" out of jealousy for her figure. Taken a step further in the manga with Jupiter.
Evil All Along: In the anime's final arc it's revealed she was working for a lecherous merman noble who has his eyes on Sun.
Gainaxing: While playing sports in Episode 17 and at the pool in Chapter 60, making her (and Sun in the latter case) the centre of attention.
Heel-Face Turn: She was a villain starting out with her mermaid exam but switches to Nagasumi's side in the anime's climax.
Heel Realization: After hearing 1/8th Figurine's warnings regarding Minamoto no Yoshiuo, she starts questioning the government's reasons for being so desperate to break up Nagasumi and Sun, and realizes she was Yoshiuo's Unwitting Pawn.
Hot Teacher: In the military academy she was a combat instructor for a short while, and schooled Maki Yuri.
My God, What Have I Done?: Has this moment in the anime's finale, prompting her Heel-Face Turn. In the manga she has another moment after confessing to Nagasumi, feeling she betrayed Sun's friendship, and later still when she realizes the truth behind the government order to break up Sun and Nagasumi.
Sarashi: Wears this instead of the bib in her school uniform, emphasizing her status as a skilled swordswoman.
Villainous Breakdown: Whenever Sun does something especially drastic, like deciding to marry a human, cut ties with her family and declare a one-woman war on the Edomae Outfit, or cross-dress as a delinquent, poor "Go-chan" is reduced to a sobbing, blabbering wreck.
Why Did It Have to Be Snakes?: He still has a fear of cats because of an incident in his childhood where a cat bit his ear while he was sleeping and he nearly lost it due to the resulting infection.
Berserk Button: Her husband's chronic immaturity and over-possessiveness regarding their daughter never fail to irritate her.
Beware the Nice Ones: Is genuinely sweet and fairly even-tempered, but make her angry and she will break you.
Carnivore Confusion: Offers Masa some fried octopus tentacle at the Bon Festival, and when he inquires whether it belongs to Nakajimanote It does. she shrugs and takes a bite out of it, to his horror.
Cherry Blossoms: When she wants to be dramatic, she makes this fall giving a speech.
Happily Married: Despite how much Gozaburo's antics anger her she really does love him. Case in point: Nagasumi once drinks a potion that makes him appear to females as whatever they think is "extremely sexy" and Ren's version of him looks almost identical to Gozaburo.
Pet the Dog: In the anime she saves the kitten from drowning despite being terrified of it, in return for it saving her from being trampled. She also expresses begrudging respect and even on rare occasions sympathy towards Nagasumi.
Poisonous Friend: For Sun. If Maki has her way, the poor girl will never have a healthy romantic relationship.
Gory Discretion Shot: The one time Fujishiro does get to eat something in the anime, namely Yoshiuo's pet giant eel and mooks, all that's seen of it is him shouting "Thanks for the meal!", the horrified expressions of Akeno and the other onlookers in the background... and enough blood painting the foreground to match the goriest of slasher flicks.
Heroic Comedic Sociopath: Nearly all his scenes involve him trying to eat Nagasumi or asking if he can eat the other students. This would make him a villain if he weren't (technically) allied to Nagasumi against people like Lunar Papa and if his antics weren't played for laughs.
Mistaken For Pedophile: When he, Masa, and Gozaburo are caught conspiring against Akeno by Ren, they come up with lame excuses based on her figure. Fujishiro remarks that he would "eat her in more than one way", causing Masa to comment on how wrong that sounds. Later, when he asks Mawari if he can "eat" her, she accuses him of sexual harassment.
Paper-Thin Disguise: One of them crossdresses in order to disguise himself and get close enough to deal with Nagasumi's cat. Unfortunately, everyone involved sees through it immediately, because it's kind of hard to disguise yourself when you look like this.◊
Implacable Man: His introductory episode is played like a (comical) horror movie with an unstoppable monster chasing the protagonist.
Lawyer-Friendly Cameo: He's is a blatant Terminator ripoff and if he weren't played for laughs (among other things) the writers might have been sued.
Made of Iron: Not even a Kill Sat can stop him. His first appearance is even called "Iron Man". He can be hurt with enough force, however.
Moe: In-universe example. In his continuing efforts to relate to Lunar, he studied gal games and learned about archetypes such as the Tsundere-Childhood-Friend and Little-Sister.
No Social Skills: He doesn't know how to communicate with people very well outside of scaring the crap out of them (especially his own daughter.)
Real Men Wear Pink: This guy is so ripped and scary that not even wearing a sailor fuku makes him any less manly.
Retired Outlaw: Wanted to go straight after Luna was born, but his wife took issue with him putting the company in front of his family.
The Stoic: The reason he's thought to be a robot is because he shows so little emotion. This is a sticking-point in his relationship with both his wife and his daughter; despite how much he loves them he has difficulity expressing it.
Why Couldn't You Be Different?: At many points they say they'd rather have a daughter than a son, to the point that they move their son to the attic and move Sun to his room.
Minamoto no Yoshiuo
Adaptation Expansion: His portrayal in the anime differs from his portrayal in the manga. At least at first.
Aristocrats Are Evil: Is the main antagonist for the anime's finale, and the manga's finale as well.
Bad Boss: Threatens to have his way with Akeno if she doesn't obey him in the anime.
Big Bad: Of the anime's finale. He's eventually revealed to be the Big Bad of the manga as well.
Crazy-Prepared: Has spies in every place even remotely related to Sun.
Dude, She's Like in a Coma: Drugs Sun into a stupor and would have raped her in the anime's finale if it hadn't been for Nagasumi.
Gonk: Is an anthropomorphic catfish, and even less human-looking than Maguro, Agitaro, and Furiyo. Partially averted in the anime, where his human form is a Bishōnen man with long blue hair.
Kaiju: Keeps an enormous eel called "Ucchan" as a pet, and has three of them in the anime.
Karma Houdini: In the anime he's infamous for drugging and raping girls who catch his fancy, but since he's a noble nobody in the merperson world can touch him until he goes after Sun and Nagasumi puts a stop to him.
Harmless Villain: In Chapter 29 of the manga he invites Sun and Nagasumi into his manor only to woo the former and try to feed the latter to his pet giant eel. After Sun pleads for Nagasumi to be spared, he apologizes and pledges his support to them, but... he lied and turns out to be Not So Harmless after all.
Mr. Exposition: Reveals to Nagasumi that Akeno is trying to break him and Sun up and that she has orders to kill him should breaking them up not work. She also reveals to Akeno that the top secret true objective of the Merpeople Examination - to break up Nagasumi and Sun - was set up by Minamoto no Yoshiuo so he could get Sun for himself.
The Nicknamer: Kept forgetting Nagasumi's name and decided to call him "Miguel" instead of "Michishio".