[[caption-width-right:237:Our lead couple, Ritsu Onodera and Masamune Takano.]]

Ah, love. There is [[TruthInTelevision truth in what people say that first love is one of the most important relationships in a person's life.]] For better or for worse.

For Ritsu Onodera, it turned his somewhat sheltered, naive 15-year-old self into an ornery 25-year-old man when his relationship with his first love went sour. After hearing his co-workers badmouth him after managing to pick up a star writer at his family's publishing company (though he had no intent on using his family connections for such a reason), he quits his job to prove he can make a star out of anyone he works with.

However, he ends up working as an editor in the shoujo manga department of his new company, Marukawa Shoten. Having decided that he would quit after two weeks, he goes into his new job with apathy only to find that his new boss, Masamune Takano, is a blunt perfectionist who tells him to leave if he was not going to take things seriously. Goaded by this, Onodera decides to stick around for the purpose of proving him wrong... all the while not realizing that his new boss was actually his first love back in high school.

''Sekai-ichi Hatsukoi'' is a BoysLove manga created by ''Manga/JunjouRomantica'''s Creator/ShungikuNakamura (the novel part is done by Miyako Fujisaki). It has also received an OVA and a series adaptation from Studio DEEN and premiered as part of the [[Spring2011Anime Spring 2011]] lineup.

Like the author's other series, Sekai-ichi Hatsukoi also focuses on several couples. The Case of Ritsu Onodera covers the main couple, Ritsu Onodera and Masamune Takano. The Case of Shouta Kisa covers Shouta Kisa, a co-worker of Onodera who also work under Takano, and Kou Yukina, a sales associate at a bookstore. And lastly, The Case of Chiaki Yoshino features Chiaki Yoshino, one of the Mangaka who works for the Emerald magazine, and Yoshiyuki Hatori, another co-worker of Onodera. Unlike the first two, which are manga and compiled under The Case of Ritsu Onodera tankobon, The Case of Chiaki Yoshino is a light novel spinoff. In October 2011, yet another novel spinoff, The Case of Takafumi Yokozawa, was released.
!!''Sekai-ichi Hatsukoi'' presents examples of:

* AllMenArePerverts: The main thing Kisa and Yukina do when they are together is have sex. Kisa reasons that it's because they're both men. A similar thing happens with Takano and Onodera. When Onodera is unsure what will happen if he goes into Takano's apartment, he replies bluntly that he's a man, what does he expect?
* ApologizesALot: Onodera ends almost every sentence he speaks to Takano with an apology in the OVA. Could arguably count as his CatchPhrase in his high school years.
* BedmateReveal: [[spoiler: Onodera freaked out after waking up in Takano's bed, [[NotWhatItLooksLike having fallen asleep on the train the night before.]]]]
* BelligerentSexualTension:
** Onodera and Takano. Nuff said, really. [[spoiler:It basically boils down to the fact that Ritsu is in recursive denial, despite the fact that he is so attracted to and in love with Takano that just holding his hand is enough to send him into meltdown.]]
** Similar situation goes for [[spoiler:Kirishima and Yokozawa]]. They fight almost as much as Takano and Onodera.
* BetterAsFriends: [[spoiler:Takano and Yokozawa. Well, Takano thinks so, anyway.]]
* BewareTheNiceOnes: hurt or hit on Kisa when Yukina's within earshot, you need to run. Really, ''really fast!''
* BishieSparkle:
** Discussed by Onodera. Also featured on screen when the Maiden Club are properly introduced.
** Yukina. His sparkling aura is so bright it hurts Kisa's eyes.
* {{Bookworm}}: Both Onodera and Takano.
* {{The Cameo}}: The guy that Ritsu worked with previously was [[Manga/JunjouRomantica Usami]]. In one chapter, Misaki is sleeping next to Onodera in the train and has also popped up in an early panel of chapter 12 when it's mentioned how [[spoiler:part-timers tally the results of the magazine surveys]].
* CharacterOverlap:
** Isaka from Junjou Romantica (and of Junjou Mistake couple) is a reoccurring minor character in this series as a Senior Managing Director of the company Takano and Onodera work at.
** Usagi appears very briefly in the first episode as one of the authors Onodera worked with while he was still working with Onodera Publishing.
** Kirishima was first introduced in ''Junjou Romantica'', helping Misaki settle in at Marukawa.
* CannotSpitItOut: Onodera watched Takano for more than three years in junior high school and high school until he randomly confessed to him.
* CentralTheme: If ''Manga/JunjouRomantica'' focuses on SecondLove, then ''Sekaiichi'' is all about FirstLove.
* CherryBlossoms: Ramp up the romantic atmosphere when Onodera first introduced himself to Takano in high school. Also illustrate Onodera's narration about how "pure" he was before he became the (self-proclaimed) jaded person of the present. And inexplicably show up ''indoors'' in ep 12.
* ChristmasEpisode: One episode is on Christmas Eve, which is Takano's birthday.
* {{Deconstruction}}: The love triangle between Hatori/Chiaki/Yanase can be seen as this especially considering the circumstance and how the characters react. Normally in a love triangle one person cannot choose between the other two and one person tends to give up for the {{Official Couple}} to be happy. However, [[spoiler: Hatori is shown to use force to get to Chiaki while Yanase cannot accept Chiaki ending up with Hatori (and thank god he doesn't know about the incident) and Chiaki constantly denies Yanase's feelings and leading him on at the same time, which causes phycological stress to build up to the point that Yanase almost makes the same mistake as Hatori only he wasn't even close to successful.]]
* DidTheyOrDidntThey: Ritsu asks Takano if they didn't anything when he was brought over to his house for one night. It doesn't help that they both were naked and Takano was very vague about it.
* EmbarrassingNickname: Isaka likes to call Onodera 'Nanahikari', which means being a kid who profits from nepotism, which irritates Onodera to no end (although he doesn't let Isaka know that). However, Isaka has a good reason for that because [[spoiler:he knows Onodera doesn't know that he only got his job at Emerald because nepotism too.]]
* ExactlyWhatItSaysOnTheTin: The title can be translated as "The best first love in the world", and "first love" is the underlying theme for all three storylines. [[NewOldFlame How it]] [[ChildhoodFriendRomance is]] [[LoveAtFirstSight played out]] is another matter.
* FishOutOfWater: The premise of the series is a literature editor getting a new job in shoujo manga department and weirded out by his in-company infamous new colleagues. He copes with it quite quickly though.
* FiveManBand: The Emerald Editors
** TheHero- Ritsu (Can be switched with Kisa during Kisa's case)
** TheLancer- Takano
** TheBigGuy- Hatori
** TheSmartGuy- Mino (After seeing in a mini comic on how he convinces his editors to finish their manuscripts)
** TheChick- Kisa (Can be switched with Ritsu during Kisa's case)
** TheSixthRanger- Yokozawa (Despite not being in the Emerald team, he does fit this trope)
* {{Funny Background Event}}: [[http://www.youtube.com/watch?v=MU0IREz3ha0&feature=related This scene]]. Watch everyone else in the background panic as Ritsu is trying to talk on the phone.
* ForcefulKiss: Subverted. Takano forced a kiss on Onodera on his first day of work just to provide a real-life example for a mangaka. Then played straight later on.
* HeadbuttOfLove: Onodera and Takano in the opening sequence of the anime.
* HeadDesk: Sekai Ichi Hatsukoi has [[http://img.photobucket.com/albums/v642/StarRose/GIFS/headdesk.gif one memorable instance]].
* IfYouEverDoAnythingToHurtHim: Happens thrice. Once when Takano tells Yokozawa in no uncertain terms that [[spoiler:he is undeniably in love with Ritsu and that if he ever hurt him or harassed him that they were through]], and afterwards when Yokozawa tells this to Ritsu about Takano. Then later it's An to Takano.
* KissingUnderTheInfluence: The first time Takano and Onodera sleep together since meeting again at Marukawa is because Onodera was drunk.
* JadeColoredGlasses: Onodera explicitly states he's jaded as a result of his first failed relationship with Takano.
* JustFriends: Takano and Yokozawa, where ([[foldercontrol]]

[[folder: Huge Spoiler ]]
) [[spoiler:Yokozawa has unrequited feelings of love towards Takano, but Takano firmly rejects him, stating clearly that he is completely in love with Ritsu and that he regards Yokozawa simply as a good friend and co-worker but nothing more. This is a very prominent ShipSinking moment, unsurprisingly.]]
* LadykillerInLove: Same-sex example. Kisa admits that he'll get in any guy's bed as long they have a handsome face and completely cut ties when he eventually gets bored of them, regardless of the other guy's feelings. Then came Yukina.
* LampshadeHanging: Befitting a story about {{shoujo}} manga editors. [[NaiveNewcomer Onodera]] comments on Shoujo tropes such as use of DramaticWind and BishieSparkle, while Takano lectures him about "maiden's heart throb page".
* LongingLook: Onodera looked for ''more than three years''. [[StalkerWithACrush He came to know a lot about Takano in that time.]]
* LoveAtFirstSight:
** Onodera falls for Takano the moment he sees him in the library. He [[LampshadeHanging berates himself a little]] for falling in love so easily.
** Kisa falls in love with any handsome guy. He did this with Yukina like his other exes but he actually falls for him seriously.
** [[spoiler: Yuu]] falls in love with [[spoiler: Chiaki at first sight when they were in middle school]] (becomes HopelessSuitor. Poor Guy)
* LoveEpiphany: The show is full of them, but Kisa's really stands out. In complete denial that he could be in love with Yukina outside of Yukina's very handsome face because he never fallen before ([[ObliviousToLove although he has been feeling a little strange around Yukina for a while]]). However Yukina points out that [[spoiler: Kisa has been avoiding looking straight at his face ever since the kiss incident in the cafe]]. Then it finally hits Kisa like a sledgehammer.
** [[spoiler: Volume 2 of the Yokozawa no baai reveals that Kirishima had one of these the night Yokozawa got drunk after being rejected by Takano.]]
** Takano as a teenager realized he was in love with Ritsu [[spoiler: after [[LaughOfLove laughing at Ritsu]] when the latter ran into a wall. Takano ''wasn't'' exactly keen on laughter as a teenager.]]
* LoveIsAWeakness: Onodera pretty much views love like this after his falling out with Takano and why he's basically fighting tooth and nail to avoid falling for Takano again.
* LoveMartyr: [[spoiler:As a teenager, Onodera was this for Takano. Case in point: Takano completely exploded and rail-roaded Onodera with an unjustified TheReasonYouSuckSpeech, and afterwards Onodera still come back in the rain to give him an umbrella he'd brought from home just in case he didn't have one.]]
* LuminescentBlush: So incredibly common with the ukes.
* MistakenAge: Kisa Shouta is 30 years old, but he certainly doesn't look it.
* MoustacheDePlume: An inverted fictional version. Yoshino writes his shoujo titles under the penname 'Chiharu Yoshikawa'. Note while Chiaki and Chiharu are technically gender-neutral names depending on the kanji, Chiharu is considered to be a more feminine name than Chiaki, which is usually a little on the masculine side. Plus only the editors at Emerald know that he's really a guy. Also a TruthInTelevision that male mangaka who work in shoujo or BL usually adopt feminine names for their works.
* {{Nepotism}}:
** What Onodera is accused of, and the reason for his low self-confidence. It is also the reason he leaves Onodera Publishing; he wishes to prove himself as a competent editor on his own.
** Isaka has this problem as well but doesn't let it get to him as much.
* NewOldFlame: Subverted with Onodera and Takano. They did not even recognize each other at first.
* NotAMorningPerson: The entire Maiden Club. It does not help that they have to work at night to meet deadlines.
* OlderThanTheyLook: Most prominent example with Kisa. Yukina thought that Kisa was a young genius editor who was around his age until Kisa tells him that he's actually 30 years old. In an extra, it's revealed that he is also the envy of the female co-workers in their company because Kisa still maintains his youthful looks even during the hectic end of the 20-day cycle (albeit he still looks kinda worn out).
* TheOneThatGotAway: Guess.
* PaintingTheMedium: Being that the main story is set in the shoujo manga department of a publishing company, Nakamura constantly makes small notes in the margins of the manga pointing out things "a mangaka ''should'' do", indicating she is prone to doing a lot of bad things herself.
* TheReasonYouSuckSpeech: Onodera gets a couple thrown his way, most prominently 1) Yokozawa when he berates Onodera for being a [[HorribleJudgeOfCharacter lazy, manipulative idiot who rides on his parents' coat-tails]] and that he has no right to even fall in love with Takano, and 2) [[spoiler:teenage Takano who takes out the frustration of his broken home on 15-year-old Onodera, telling him that he sucks for loving him like he does, and furthermore that he's incredibly annoying and 'seriously gross']]. Remember those self-esteem problems that Ritsu had and his issues believing that Takano really loved him in the first place? Not helping.
* RidiculousProcrastinator:
** The source of misery for the editors.
** Yoshino is pretty infamous among the Emerald crew since he seems to have a lot of trouble getting his manuscripts on time because of this. Poor Hatori constantly has to make him get it to the printing department on the nick of time because he can predict Yoshino's patterns due knowing Yoshino since they were kids.
* RunningGag: Yukina saying/asking something extremely surprising or inappropriate, causing Kisa to [[SpitTake spit take]] his coffee.
* SelectiveObliviousness: Takano accused Onodera of this when the latter could not remember the details of their break up.
* SelfDeprecation: A running gag in the series is that mangaka cannot finish their work on time. Also, though mostly in the Yokosawa novel, the author notes about how weird the BL department is.
* SempaiKohai: Takano and Onodera's relationship in highschool. And in the present, Takano is Onodera's sempai at work.
* SequentialArtist: Considering it focuses on the manga publishing industry, a lot of these show up in the cast and the non-romance plot revolves around managing them.
* SexyDiscretionShot: This is used so often in the anime adaptation that it would be difficult to name every instance of it.
* SleepCute: Onodera fell asleep on the train and used Takano as a pillow (though not intentionally). [[BeautifulDreamer Takano didn't mind.]]
* SnowMeansLove: In the ending sequence. [[spoiler: And in the manga, Onodera and Takano went on a date for Takano's birthday and it snowed]]
* StylisticSuck: Averted. The manga manuscripts in the anime look like actual manga.
* SuspiciouslySpecificDenial: Onodera's [[OverlyLongGag "This is definitely not love"]] over several episodes.
* {{Too Dumb to Live}}: [[RuleofThree Chiaki...Chiaki...Chiaki!!!!]]
* TwoLinesNoWaiting: The whole series consists of four independent stories with some overlap with each other, most noticeably that all characters are affiliated with Marukawa Publishing one way or another.
* UnequalPairing
* UnrequitedLoveSwitcheroo: Ritsu and Takano.
* [[BathroomStallOfOverheardInsults Vending Machine Of Overheard Insults]]: Onodera overheard his co-workers badmouthing him and accusing him of using his family connections to become Akihiko Usami's editor, which is why he quit.
* VitriolicBestBuds: Yokozawa and Takano are good friends. Their first scene in the anime together, however, is an insult match.
* WhatDidIDoLastNight: In the manga, and now the anime,[[spoiler: Ritsu gets drunk and ends up partially-confessing and sleeping with Masamune (his current boss and former boyfriend). He does not remember ''any'' of it the following morning, despite waking up in his bed and feeling very, er, sore, afterwards. He suspects but is in complete denial, much to the great annoyance of Masamune, who has been trying to get him to admit that he likes him for ''months''.]]
** Yokozawa has a bit of this too [[spoiler: when he wakes up after a night of drinking and finds he shared a hotel room with Kirishima]].
* WillTheyOrWontThey: Onodera and Takano from episode 2 of the anime onwards.
* WorkCom
* YoungerThanTheyLook: Yokozawa who gets teased for looking like he's in his early thirties despite being only 28.