History Characters / HekikaiNoAiOn

* TomboyishPonytail

* MostCommonSuperpower: All the mermaid have big breasts except Bella, who's flat as a table.

** IGotBigger: Though 9-years-old Tatsuya looks quite the same as 16-years-old Tat-chan, just bigger.

* BigBrotherMentor: To Tatsuya; who calls him "Tsukasa-[[JapaniseHonorifics niisan]]".

* BigBrotherMentor: To Tatsuya; who calls him "Tsukasa-[[JapaniseHonoifics niisan]]".

** ConvenientlyAnOrphan

* ParentalAbandonment: His parents died a week before the start of the story.

** ShooTheDog: ...but Seine went back to him, right at the middle of the fight, so he told her to go to a safer place away from the sea.[[spoiler: Sadly, this distracted him enough that the mermaids were able to attack him and eat him.]]

Yuzuki is Shizuki's younger sister. She is the polar opposite of her sister: she has superhuman strength, is diligent and a good cook, but is a little dumb. She is good-hearted and carries out her Onee-sama's orders. She also has an immortal body and has lived for centuries. She is a Lolicon (she gets excited by children, especially girls) to the point of kissing every child she meets on the mouth upon first sight.

* AttackOfThe50FootWhatever: Ariel.

* ImTakingHerHomeWithMe!: Yuzuki seems to have this sort of reaction to every small, cute child she sees.

* I'mTakingHerHomeWithMe!: Yuzuki seems to have this sort of reaction to every small, cute child she sees.

* IGaveMyWord: When she found someone who [[PleaseDontLeaveMe asks her to stay by his/her side,]] she stays until they die, tell her to leave, or obstruct her revenge, [[spoiler:because she used to be completely alone, too.]]

* IGaveMyWord: When she found someone who [[PleaseDontLeaveMe asks her to stay by his/her side,]] she stays until they have someone else to rely on, [[spoiler:because she was once the same as them.]]

* IGaveMyWord: When she found someone who [[PleaseDontLeaveMe asks her to stay by his/her side,]] she stays until their last day [[spoiler:because she was once the same as them.]]

* ImportantHaircut: She used to have a mild example of RapunzelHair, but she cut it when she ultimately decided follow the YouKilledMyFather path.

* PolarOppositeTwins: with Yuzuki

** [[spoiler:TheBusCameBack]]: in chapter 40.

She was introduced as a new transfer student; and Tatsuya is given the assignment of teaching her sign language. [[spoiler:The youngest of the mermaids; she is despised by all her older sisters except for Ariel. Seine thought she had killed her some 300 years before, but Ariel restored her body almost entirely, leaving her badly scarred about the neck and unable to talk, but with the ability to change herself to have legs and walk about on land. Her true goal is infect a lot of people to order to take revenge on Seine for leaving her without her voice.]] She falls in love with Tatsuya.

[[TimeSkip Four years later]] she stills meets Tatsuya as he promeses her [[spoiler:for stop thinking of avenge herself]] but [[spoiler:she's discovered by two of her sisters and leaves the sea in fear. Tatsuya took her into his house even though Seine is there; Seine allows she lives there but as a host against her sisters]]. She seems very jealous of Seine for being target of Tatsuya's affections.

** After 4 years, [[spoiler:she evolved to [[SlidingScaleOfAntiVillains Type 4]]]] since she still hate Seine.

* BecauseYouWereNiceToMe: She ordened [[spoiler:to the infected humans]] to [[YouWillBeSpared do not hurt Tatsuya]] because he was nice to her.

* BlessedWithSuck: [[spoiler: She has the ability to turn her tail into legs and move around on land but can't go far afield the ocean]]. See HeroicRROD below.

* CryCute / InelegantBlubbering: She does [[http://www.mangareader.net/1646-52654-10/hekikai-no-aion/chapter-16.html one]] or [[http://www.mangareader.net/1646-52654-11/hekikai-no-aion/chapter-16.html another]]

* FishOutOfWater: [[spoiler:Quite literally; since she starts living in Tatsuya's house]]
* ForcefulKiss: [[spoiler:The way she infects humans at land]]
** [[spoiler:At the end of chapter 38, she gives one of this to Tatsuya.]]

* GoingCommando / VaporWear: She seem to doesn't know what a bra is or for what is used.
* HeroicRROD: [[spoiler:If she overstay at land, Sheila's body will start to painfully rot, because her body is a human corpse from neck down. She just can live safe in the sea]]
* IdenticalStranger: with Tatsuya's mother, who happens to be called Umi. The reasons of this have not being revelated yet.

* InSeriesNickname: Shii-chan

* NonHumanSidekick: Anna the sea slug was this for her, aside her only best friend

* SchoolUniformsAreTheNewBlack: Sheila is always showed wearing her uniform [[spoiler:Justified; it seems to be her [[LimitedWardrobe only wardrobe]]]]

* SingleWomanSeeksGoodMan: Sheila fell for Tatsuya because he was the only aside her sister to show her kindness.
* SproutingEars: or Sprouting Dog Tail in her case
* TalkingWithSigns: She carries around a notebook where she writes what she wants to say; also, she learns some HandSignals from Tatsuya
* [[spoiler:UnusualEars: As a mermaid]]

Simon was Seine's third foster father and the one person who showed her kindness when she was young. He was known as a magician in his time and was also known to be 1700 years old (about 300 years ago in present time of the story). He bore the "Aion" mark, just like Seine does at the present time, but he had it across the right shoulder, and was able to use Aion's power for his own, unknown, reasons. [[spoiler:He died eaten by the mermaids]]

* BecauseYouWereNiceToMe: Seine decided go with him because Simon was nicer to her than her current foster father
* BigOlEyebrows: In comparison to the rest of the cast

* DissonantSerenity: Since he's {{Immortal}} and knows [[GoodThingYouCanHeal his wounds can't be fatal]], he's always cheerful even in front of danger

* FaceFramedInShadow: Until his formal introduction

* ItsNotYouItsMyEnemies: Tried to leave Seine in somewhere safe without telling her before he went to fight the mermaids.
** ShooTheDog: But Seine went back to him, right at the middle of his fight with the mermaids, so he told her to go to a safer place away from the sea.[[spoiler:..distracting him enough time to the mermaids attack him and eat him]]
* LikeAGodToMe: Seine quoted this trope word-by-word to describe her admiration and love to Simon.
* ParentalSubstitute: to Seine

* SpellMyNameWithAnS: Some translations write his name as "Shimon", being Shimon the japanese pronunciation of Simon.

They are Seine's prey, in revenge of Simon. In-universe, they are the ones who sank Atlantis and Mu, destroyed Pompeii, Italy and sank Port Royal, Jamaica in orden to collect psyche from humans. Until now, 5 of the 7 mermaids had being introduced. They are Ariel the eldest, Bella the second, Enati the third, Anshu the forth and [[spoiler:Sheila the seventh]].

* BerserkButton: [[BigSisterInstinct Hurting or bulling her youngest, little sister]] is this to Ariel.

* [[BigBrotherBully Big Sisters Bullies]]: to their youngest sister except for Ariel.

* TheBrute: Bella. She's sadistic, ruthless and loves to cause pain.

* MostCommonSuperpower: All the mermaid had big breasts except Bella, who's flat as a table.

* BerserkButton: Shizuki and Yuzuki. Also anything mermaids relevant.
* BrokenBird: [[spoiler:The first 4 years of her life were horrible, her ParentalSubstitute was killed in front of her and she had seem lots of people she cared about dying at their time]]
* {{Delinquent}}: She's seem as this by Tsukasa
* EveryoneCallsHimBarkeep: Seine is frequently called a witch instead of her real name.
* EvilEye: While using Aion
* EyesOfGold / HazelEyes: Normally
* {{Expy}}: of {{Karin}}, appearance only though

* HarukaTomatsu: Her Drama CD VA
* HugeGuyTinyGirl: with 19-years-old Tatsuya

* IGaveMyWord: When she found someone who [[PleaseDontLeaveMe ask her to stay by his/her side,]] she stays until the last day [[spoiler:because she was once the same as them.]]

* ImportantHaircut: She used to had a mild example of RapunzelHair but she cut it when she ultimately decided follow the YouKilledMyFather path
* InnocentFanserviceGirl: or more like "Doesn't care fanservise girl".

* LeParkour: With Aion's help. Tatsuya even compare her with a jumping roofs's cat
* {{Neet}}: After TimeSkip
* NotGrowingUpSucks: Seine had to hold up being in high school who knows how many times! She even complains about it while talking about her nth school's festival.

* ParentalAbandonment: [[spoiler:She doesn't know anything about her biological parents]]

* SuperDrowningSkills: Seine can't swim. Even in a kid's pool with floaters, she sink like a rock; and she fights the people of the sea. The irony.
* TeensAreShort: her height is 1.46m (4' 7")
* TheNoseKnows: She claims infected humans have a different smell than normal humans and she with the time learned how distinguish it

* WhenSheSmiles: [[http://www.mangareader.net/1646-52658-31/hekikai-no-aion/chapter-20.html Just look at her]]. [[DoggedNiceGuy Tatsuya]] is out of breath

* YouKilledMyFather: Her {{Revenge}} motivation
* ZettaiRyouiki: Grade B and sometimes Grade A

After the death of his parents in a car accident, Tatsuya tries to live to fulfill his father's last wish of becoming a "high caliber" man. After "saving" Seine from bullying, he insist on trying to help her, even after finding out the real goal of Seine. He is kind, optimistic and believes in other people's good side which is sometimes an obstacle in Seine's revenge. He is a bad cooker but somehow Seine is not bothered by his food. He has a crush on Seine and wants to be acknowledged as a "high caliber" man by her.

[[TimeSkip Four years later]] he starts going to University at the city.

* AccidentalPervert: Luckly for him, the girls are an IceQueen and a FishOutOfWater.

* BecauseYouWereNiceToMe: After Seine [[PetTheDog pet him]] saying he can become a "high caliber" man, he fell for her and wants to be acknowledged by her.
* TheBigDamnKiss: [[spoiler:Finally the guy gather courage and give one to Seine in chapter 39]].
* {{Bishounen}}: First the cute kid edition, then later the hot guy edition
* BreakTheCutie: Let's just say chapter 15 wasn't very nice to him. He get better at the end of chapter 16 with Seine's help.
* DoggedNiceGuy: to Seine
* DraggedIntoDrag: forced to dress up as a {{meido}} as part of his class's cafe staff. And the girls rejoiced.
** AttractiveBentGender: ...but no one can't deny he looks so cute as a female.
* HeroicBSOD: At his parents's funeral. [[JustifiedTrope Understandable]].
* InTouchWithHisFeminineSide: He tries to take care of his house once since his uncles left: make meals, clean and stuff. Minato jokes that he acts like a wife.

* LethalChef: As [[IllGirl Shizuki]] [[BloodFromTheMouth discovered]]. Only Seine is not bothered by his food
* LivingEmotionalCrutch: He became more or less this to Seine after [[spoiler:his JourneyToTheCenterOfTheMind of Seine and learning why she's so broken]]. He promesed her to always be there for her and, as a bonus, he reminds her of a past friend.
** KidWithTheLeash: He's also the only one able to control and stop Seine when she's in a rampage rage. [[spoiler:Also, he could be this to Sheila too.]]
* LonelyRichKid: until Seine promeses him to stay.
* MamikoNoto: His Drama CD VA

* NiceGuy: Initially
** TheMessiah: He evolved to this, [[spoiler:he stopped Seine of killing Sheila and convinced Sheila to desist in her revenge]] but...
*** StupidGood: Seriously Tatsuya [[spoiler:Who in their sane mind puts a mermaid to live under the same roof as Seine]] just because you like them both!?

* OneHeadTaller -> HugeGuyTinyGirl: with Seine

* ParentalAbandonment: His parents died a week before the start of the history

* SingleTargetSexuality: upon Seine
* TeensAreShort: 1.62m (5' 4") at the age of 16
* WaterWorks: He cries a lot
* YouAreNotAlone: to Seine.

Nagisa is a girl in Tatsuya's class, a long time acquaintance, and would probably like to get closer to Tatsuya, but ever since Tatsuya found a lost puppy (soon to be Crokette) Nagisa has had violent allergic reactions when ever she is in Tatsuya's house. So she simply stays away from him, even though she loves him.

* BerserkerTears / BrokenTears: Cried this while [[spoiler:[[BrainwashedAndCrazy choking Seine to death]]]].
* CanNotSpitItOut: She just can't say: "Tatsuya, I Love You"
* ControlFreak: Mild example. Since she is in charge or her house, she's very stric even with her [[BumblingDad father]]
* DamselInDistress: [[spoiler:when she was infected by Mushis]]
* {{Expy}}: Of Maki from {{Karin}}
* ExpositoryHairstyleChange: After TimeSkip, she's seen with a BobHaircut instead of her long side ponytail.

* FirstNameBasis: With Minato. She also uses to had this with Tatsuya, but since everybody thought she was [[{{Golddigger}} taking advantage of him for being rich]] and her allergies, she's starting to keep her distance.
** They get back to the first name basis after [[spoiler:the Mushi incident]]

* HeroicSelfDeprecation: She thinks she's a bad, selfish person, unworth of {{messiah}} Tatsuya. She gets better.
* LikeAnOldMarriedCouple / ShipTease / BelligerentSexualTension: with Minato.

* MoreThanMindControl: [[spoiler:When she was infected by Mushis]] they use her jealousy to Seine and her fear that Tatsuya knows she wanted his dog dead to break her will

* SingleWomanSeeksGoodMan: She fell for Tatsuya when he defended her from acussations of being a golddigger.

* WeaksauceWeakness: She's allergic to dog's hair.

** ShinyMidnightBlack: with purple undertones.

Tatsuya's friend and Nagisa's neighbor. More world-wise than his friend and more savvy, he notices that Seine is not a normal girl.

* BoyNextDoor: To Nagisa, and he knows how milk the situation, always inviting himself to breakfast at her house.
* TheConfidant: He's the only who Nagisa can talk about her crush on Tatsuya and her allergy to dog's hair.

* {{Foil}}: to Tatsuya.

* LikeAnOldMarriedCouple / ShipTease / BelligerentSexualTension: with Nagisa.

* PermaStubble: after TimeSkip.

** TallDarkAndSnarky: in some degree
* ThoseTwoGuys: with Nagisa.

** BreakTheCutie: Chapter 3 and 4 did this to her but thanks to LaserGuidedAmnesia as ResetButton, it was like this never happened.

* HairColorDissonance: Is she a brunette or a dirt blonde? Or even a strawberry blonde?
* HilariouslyAbusiveChildhood: Sorta. Her father wants her to [[KissingCousins marry Tatsuya]] to get hand at his heritage to pay his debts; she declares [[ParentalNeglect her parents barely pay attention to her]] and just worry about money, and [[ParentsAsPeople when they try to care, they just ashame her]]. All PlayedForLaughs.

* TokenMiniMoe: and first victim of Yuzuki's ForcefulKiss.[[spoiler:..at least on this time]]

A protege of Tatsuya's father. He and Tatsuya have a fraternal relationship, even though they are not blood relatives. He cares and looks after Tatsuya but his job as a lawyer prevent him of being able to be close to him.

* CloserToEarth: He says to Tatsuya that he can't go around, picking girls to live in his house. [[RealityEnsues And he's right]].
* LikeBrotherAndSister: Non-romantic way. He has no blood tie with Tatsuya or Minagi but he's a member of the family.

* MenDontCry: {{Averted}}. He breaks to cry everytime Tatsuya acts as a delinquent on his eyes.

* NoIndoorVoice: Most of his dialogue are yellings towards Seine or Tatsuya, usually crying.

* OlderThanHeLooks: He looks like in his early 20, but it's 27. After TimeSkip, he looks practically the same but now he's ''31''.

Shizuki is the older sister of the "Akuma Twins". Being the older, she is sarcastic, lazy and smart but she has a weak body (She can get sick and tired easily, she cannot swim in pools because of the chlorine and Tatsuya's food almost killed her). She has an immortal body and has lived for centuries. She gave immortal bodies to Seine and Simon. Her former name was "Pistis Sophia" but she changed because it was "stupid". She is a Oyaji-con (she is attracted to "handsome" grown up men).

* AffectionateGestureToTheHead: To Yuzuki. Also sometimes to Seine just to annoy her.

* CovertPervert: she's an "Oyaji-con", she likes [[GrandPaWhatMassiveHotnessYouHave old, handsome men]]

* IllGirl: Her body is so weak that she can't swin in pools because of the chlorine, gets tired easily and Tatsuya's food [[BloodFromTheMouth almost killed her]]. Luckly she's immortal.

* MeaningfulName: Shizuki means "Calm moon"

* MulticoloredHair: Black with blonde bangs
* {{Neet}}: she does absolutlely nothing but eat and sleep. Justified for being an IllGirl

** [[spoiler:TheBusCameBack]]: in chapter 40.

* ShowSomeLeg: in Volumen 4's index

* ThemeTwinNaming: With Yuzuki

Yuzuki is Shizuki's younger sister. She is the opposite side of her sister: her body has superhuman strength, she is diligent and a good cooker but is a little dumb. She is good hearted and satisfies her Onee-sama's orders. She also has an immortal body and has lived for centuries. She is a Lolicon (she get excited by children, especially girls) to the point to kissing every children on their mouth upon just seeing them.

* BoobsOfSteel: the physically strongest character in the series and one of the bustiers

* BridalCarry: Sometimes she carries Shizuki around like this

* TheDitz: Shizuki even said that Yuzuki is just a kindergarden's girl in her mind

* ExtremeDoormat / TheCaretaker: to her sister
* ForcefulKiss: the way she express her [[{{Lolicon}} love]] for little girls. '''Any''' little girl

* IdenticalTwinIDTag: She's the one with the LittleBlackDress [[MiniDressOfPower Of Power]]

* {{Lolicon}}: PlayedForLaughs and LesYay
* MeaningfulName: Yuzuki means "Kind moon"

** Bikini at the PoolEpisode
** Her {{Meido}} outfit at "work"

* MulticoloredHair: Black with blonde bangs
* NoSenseOfDirection: She gets lost inside a school; mostly because of her ditzness and the insides of the school are too complex to her

* PolarOppositeTwins: with Shizuki

* PrettyFreeloader: But at least, she cleans and cook

* HilariouslyAbusiveChildhood: Sorta. Her father wants her to [[KissingCousins marry Tatsuya]] to get hand at his heritage to pay his debts; she declares [[ParentalNeglect her parents barely pay attention to her]] and just worry about money, and when they try to care, they just ashame her. All PlayedForLaughs.

* HilariouslyAbusiveChildhood: Sorta. Her father wants her to [[KissingCousins marry Tatsuya]] to get hand at his heritage to pay his debts, she declares her parents barely pay attention to her and just worry about money, and when they try to care, they just ashame her. All PlayedForLaughs.

* AccidentalPervert: Luckly for him, the girls are an EmotionlessGirl and a FishOutOfWater

* {{Meido}}: She works as a maid in Tatsuya's house

** {{Meido}} outfit at "work"