[[quoteright:320:http://static.tvtropes.org/pmwiki/pub/images/umi_monogatari.jpg]]
[[caption-width-right:320:Kanon, Urin & Marin]]

Originally a pachinko game series, ''Umi Monogatari'' (''Sea Story'') was given an anime adaptation by {{Creator/ZEXCS}} in the summer of 2009 with the subtitle ''Anata ga Ite Kureta Koto'' (''That You Were There for Me''). It was directed by Creator/JunichiSato.

Under the sea, two mermaid sisters by the name of Marin and Urin are enjoying their life devoting full time to floating. One day, a ring falls from the surface and into Marin's hands. She wants to find the ring's owner and return it, and takes Urin along for the ride. It's then that they run into Kanon Miyamori, a young priestess who's about to get involved in a series of events neither she nor the sisters could've planned for when Urin ends up unleashing Sedna, an evil force intent on shrouding the world in darkness. This is what prompts Marin and Kanon to become the Priestess of the Sea and Sky.

''Umi Monogatari'' is unusual among MagicalGirlWarrior shows in that the focus is more on emotional development of the characters, the fights are fairly long, the girls' mentor is completely wrong about some things, most of the music is gentle piano music, and the revelation of what the BigBad ''really'' is allows for a conclusion that's more true to life than most shows of this nature.
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!!Tropes in ''Umi Monogatari'' include:

* AllLovingHero: Marin sincerely proclaims that she loves everyone she meets. Her hug will save the world.
* AlphaBitch: Oshima, who acts haughty around Kanon and is obsessed with winning Kojima. However, she has HiddenDepths.
* AnAesop: [[spoiler: Everyone has darkness in their hearts. That's normal, and we must learn to accept it, not cast it out]].
* {{Anticlimax}}: [[spoiler: There is no final battle, as Sedna's nature and the accompanying sorrow is accepted by the islanders rather than sealed away]]. There is, however, an emotional battle to save [[spoiler: Urin]].
* ArcWords: "I love you!" crops up very frequently throughout the story as Marin and her relationships change.
* AuraVision: Kanon has an "evil aura" that everyone can see and comment on.
* BalanceBetweenGoodAndEvil: This turns out to be a crucial part of the series, as [[spoiler: the islanders' unwillingness to accept and deal with the sorrow in their hearts created Sedna]]. In the end [[spoiler: the darkness is accepted by them and becomes one with the light]].
* BareYourMidriff: It's standard for Mermaids, but Oshima and Miyako are prone to this as well.
* BittersweetEnding: [[spoiler:Kanon and Marin defeat Sedna, but have to separate since land and sea people are not supposed to be together. It is hinted that Kanon will keep looking for Marin]].
** In the DVD special it becomes clear that [[spoiler:Kanon keeps longing to meet Marin again. She even seems to get her wish for a while, which makes things even more bitter]].
* BladeOnAStick: The girls are told that to seal Sedna away they must pierce her with the Spear of Light. [[spoiler: It's never seen, as they defeat Sedna and save Urin another way]].
* BonusEpisode: The bonus 13th episode in which [[spoiler:Marin and Kanon have a near-encounter after the series]].
* BrainwashedAndCrazy: Sedna does this to sea creatures and eventually [[spoiler: Marin and Kanon's friends]].
* BrattyHalfPint: Urin is this mainly towards people on land.
* ButterflyOfDeathAndRebirth: Eerie blue butterflies show up the night of the eclipse. [[spoiler: Urin grows butterfly wings after hatching from a cocoon]].
* CannotSpitItOut: Kanon doesn't confess that she likes Kojima because she's afraid he'll reject her.
* CantCatchUp: Kanon struggles with this, feeling inadequate at times.
** Urin does likewise to a much greater extent, as she can't fight at all, but wants to very badly.
* {{Catchphrase}}: "I love you!", said by Marin to almost everybody.
* CerebusSyndrome: Sets in around episode 6, coinciding with the eclipse and [[spoiler:Urin being corrupted by Sedna]].
* ClingyJealousGirl: Urin is this towards Marin, becoming jealous and scared about Kanon's intrusion and worried it will shatter their sisterly bond. Justified since she's a little girl.
* TheCorrupter: Sedna corrupts the islanders, sea creatures, and [[spoiler:Urin]] to suit her needs.
* TheCorruptible: Various sea creatures, but this trope is most present in [[spoiler:Urin]].
* TheCorruption: Sedna's influence, signified by too-bright or red eyes.
* DarkAndTroubledPast: Everyone was afraid of Kanon as a child due to her evil aura, which made her grow up aloof and unwilling to trust herself and others.
* DarkIsNotEvil: Kanon's evil aura doesn't make her evil; it grants her immunity to Sedna's evil.
** This is the point of the shrine maiden's song, as darkness and light must coexist.
** In the end, [[spoiler: Sedna fits this, as she was created out of accumulated sadness in people's hearts]].
* DarkestHour: The end of episode 11. Marin and Urin ''try'' to fight Sedna, but have their powers drained from them. The episode closes with them sprawled on the ocean floor, near death, as Sedna's darkness flows into their bodies.
* DefrostingIceQueen: Kanon starts out aloof, awkward, and unwilling to form connections with people. However, she gradually warms up to Marin.
* DesignatedLoveInterest: Kojima, with whom Kanon doesn't even have a fraction of [[RomanticTwoGirlFriendship the chemistry she has with Marin]].
* DisabilityImmunity: Kanon's evil aura protects her from Sedna's darkness.
* DoesNotLikeShoes: Most underwater citizens, including the two main characters, will go barefoot, unless trying to remain inconspicuous and wearing more conventional clothes of the "sky people."
* DrowningMySorrows: Not in alcohol, but in a soothing song the island priestess sings; it even calms Marin out of her HeroicBSOD. [[spoiler: And the ocean. The islanders' tears and a ritual involving tossing stones that represented their sorrow into the sea formed Sedna out of their collective grief]].
* EarnYourHappyEnding: Marin, Kanon, and Urin have to go through a lot while fighting Sedna, including facing their own fears and [[spoiler:being corrupted by the darkness]]. In the end they [[spoiler:don't destroy Sedna, but accept her and their sorrow back into their hearts, melting the darkness with light]].
* EverybodyLives: Despite numerous warnings of death should specific actions be taken, no one dies at the end of the series.
* FaceHeelTurn: [[spoiler: Urin]] turns evil halfway through the series.
* FantasticRacism: Urin's not exactly pleased with the people on land, and often wishes to return to the sea.
* {{Flanderization}}: Everyone's traits were exaggerated in the OVA.
* {{Foil}}: Marin is outgoing and positive, while Kanon is quieter and gloomy.
* {{Gainaxing}}: Oshima invokes this to get Kojima to notice her, only to be quickly outdone by Marin.
* GenkiGirl: Kanon's mom, Miyako, is perky and lively.
* GetAHoldOfYourselfMan: Oshima tells Kanon to stop her half-hearted attempts and face her without hesitation, galvanizing Kanon to do better.
* GreekChorus: The shrine maiden comments on the plot at times, and her song delivers clues to its resolution.
* TheHeartless: [[spoiler:Sedna fits this, being born out of the people's sorrow]].
* HeroicBSOD: Marin goes through one in the latter half of the series, causing her to be unable to transform.
* HopeSpot: In episode 11, Marin and Kanon try to combine their powers to save Urin from Sedna. She just absorbs it, draining them completely and shattering their [[TransformationTrinket transformation stones]].
* HumanityEnsues: Any sea creature Sedna corrupts takes on a human form.
* IncorruptiblePurePureness: The Elder Turtle thinks Marin is this, and strives to protect her from the darkness. [[spoiler:Instead she falls into it]].
* {{Iyashikei}}: This anime is about accepting your inner darkness.
* InnocentFanserviceGirl: Marin's skimpy clothing is commented on when she first comes ashore, though Kanon eventually gets her and Urin to wear something a little less revealing.
* KissOfDeath: Sedna's soldiers try to kiss Kanon to suck out her evil soul.
* KnowNothingKnowItAll: The Elder Turtle has shades of this; not only is he wrong about [[spoiler: which priestess will fall into darkness]], he doesn't comprehend what Sedna truly is and gives wrong information as a result.
* LastEpisodeThemeReprise: Inverted, as the theme plays at the beginning of the last episode in a more somber tone as [[spoiler: Marin and Kanon are near death]].
* {{Leitmotif}}: The [[http://www.youtube.com/watch?v=Nwx0gJwNa-Y shrine maiden's song]], as well as [[http://www.youtube.com/watch?v=NFNTGlR9tsM Sedna's theme]].
* LonelyPianoPiece: This constitutes a lot of the music in the series.
* MadeOfEvil: [[spoiler:Sedna, though not so much evil as sadness]].
* MakingASplash: Marin's power is to control water.
* MeaningfulName: Sedna takes her name from an Inuit sea goddess, fitting the oceanic theme.
* {{Miko}} {{Magical Girl Warrior}}s: Marin and Kanon.
* MonsterOfTheWeek: The first few episodes have Marin and Kanon battling creatures that Sedna summons. This pattern gets abandoned halfway through the series as it focuses on more personal battles.
* MoodWhiplash: Setting in from the solar eclipse episode onward. What was once a happy, gentle show takes a turn for the scary.
* MumLooksLikeASister: Miyako, Kanon's mother. She looks young enough to be one of her daughter's friends, and has the personality to match.
* NiceJobBreakingItHero: Urin lets Sedna's sky half out while looking for the ring, and Kanon threw the ring away in the first place.
* NotNowKiddo: Urin suffers this as Marin talks more to Kanon, which causes a rift between them.
* OlderAlterEgo: A villainous version. [[spoiler:In the final episode, Sedna possessing Urin causes her to age into a young woman]].
* OnTheNext: Next episode previews generally have Marin talking about sea creatures.
* OnTheNextEpisodeOfCatchphrase: Marin's "Everyone, I love you!"
* OpenMindedParent: Two mermaids and a talking turtle staying at Kanon's house? No problem!
* OurMermaidsAreDifferent: Aside from the natural ability to breathe underwater, the sea people are almost exactly like humans.
* PlayingWithFire: Kanon's power is to control fire.
* PowerDyesYourHair: Kanon's hair becomes lighter and has a different shape when transformed.
* PowerGivesYouWings: [[spoiler: Urin]] appears with a pair of butterfly wings after she awakens from a literal cocoon. In the final episodes the wings grow huge and colorful.
* PowerMakesYourHairGrow: Marin and [[spoiler: Urin]] get this when transformed.
* ThePowerOfLove: This is how Marin and Kanon save Urin from Sedna. [[spoiler:Instead of defeating Sedna with a spear of light and killing Urin, her host, Marin and Kanon reach out to her. They hug her, and the power of Marin's love and Kanon's acceptance of darkness moves Sedna's heart and causes her to disappear peacefully]].
* PrehensileHair: Two Monsters of the Week have this, using their hair to tie up and strangle Kojima. They nearly kill him before being defeated.
* RealPlaceBackground: The island Kanon lives on is modeled after one of the Japanese islands of Amami-Oshima, which gets mentioned in the DVD special.
* RedEyesTakeWarning: Averted with Kanon and the shrine maiden, but played straight with [[spoiler: a corrupted Urin]].
* RedHerring: The Elder Turtle is often wary of Kanon and is convinced she will fall into darkness if not watched. [[spoiler:He's wrong. Marin does]].
* RedemptionEqualsDeath: [[spoiler:Urin believes this in the finale, but she's convinced otherwise and saved]].
* RefusalOfTheCall: Kanon is awkward about her powers and would rather not have to use them.
* TheReveal: Kanon and Marin find out about Sedna's true nature while being almost defeated by her. Specifically, [[spoiler:Sedna is formed from the combined sorrow that the inhabitants of the island committed to the sea]].
* RomanticTwoGirlFriendship: Curiously, Marin and Urin's relationship seems to swing that way, despite their age difference.
** Also between Kanon and Marin.
* SatelliteLoveInterest: Kojima, who never gets much more background than that Kanon likes him.
* SealedEvilInACan: Sedna was sealed away in the sea and on land.
* SealedEvilInASixPack: Sedna; she has half of her in land and half in the sea.
* SceneryPorn: Plenty of lovely shots of the seaside town in which the story takes place.
* SheatheYourSword: [[spoiler: Sedna is "defeated" by everyone accepting the darkness within them, not casting it away or fighting it]].
* ShootTheDog: The Elder Turtle lives by this, even telling the girls to take him down without hesitation should he be corrupted. More disturbingly, he also tells them to not hesitate in killing Sedna, which would also [[spoiler:kill her host, Urin]].
* ShoutOut: To "Literature/TheLittleMermaid", as [[spoiler: Marin is warned that Urin will turn into sea foam once Sedna is defeated. [[EverybodyLives She doesn't]]]].
* SugarApocalypse: Seen in the latter half of the series, as the formerly tranquil island and ocean begin to be corrupted.
* SymbioticPossession: In the second half of the series, [[spoiler:Urin and Sedna's relationship works like this. Urin gets Sedna's powers, while Sedna gets her body]].
* TakingYouWithMe: In the finale, [[spoiler:Sedna tries this on her host body, Urin]].
* TentacleRope: Kanon is bound by an octopus woman's hair-tentacles in episode 2.
* TotalEclipseOfThePlot: The solar eclipse triggers [[spoiler: Urin's FaceHeelTurn and Marin's HeroicBSOD]].
* TrailersAlwaysSpoil: The trailer spoils [[spoiler: Urin turning evil]], though in a different fashion than what happens in the show.
* TransformationSequence: Marin and Kanon each get a short one.
* TreasureMap: Marin and Kanon go in search of treasure, but end up finding angry pirates.
* UltimateEvil: Sedna has no real form, and is only seen as shadows and a cloud of red sparkles.
* UnreliableExpositor: The Elder Turtle is completely wrong about a lot of things.
* VocalDissonance: Kojima sounds ''very'' girlish despite being a studious young man..
* VolcanicVeins: Those corrupted by Sedna have these, particularly on their legs, arms, and face.
* YouGottaHaveBlueHair: Kanon's hair is a dark blue color, but becomes a lighter tone when she transforms. Played straight with Warin.
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