Ao no Flag has the situation between the main characters. Taichi is playing The Matchmaker for the shy Kuze and his Childhood Friend Mita. He starts falling for Kuze, who is interested in Mita and Mita is apparently interested in Taichi. Kuze's closest friend, Itachi, is in love with her as well.
Maison Ikkoku. Until the final season which finally untangles the complex relationships virtually all the love is unrequited. Even poor Kentaro (a minor character, the ten year old Only Sane Man) doesn't escape it. The first season ending song exemplifies the angst that can develop from this trope. Although in this series all of Takahashi's characters get a happy ending.
Ranma ½: According to Rumiko Takahashi, this is because all the side characters in the Love Chart were merely obstacles to Akane and Ranma's eventual hook up. Yes, even Mousse. The only reason Ryōga became the lone exception was because the fans demanded his happiness.
In Urusei Yatsura this accounts for every single romantic relationship, and at least half of all interpersonal relationships of any sort. And even if it isn't (the rare examples being Tsubame and Sakura and, eventually, Inaba and Shinobu), the rest of the craziness conspires to keep them apart. Arguably, Ataru and Lum also love each other, but analyzing that would require a separate page altogether. Even the author had to do it in the last volume of the latest version of the manga
Video Girl Ai is filled with this, just about every character has a case of this. It's done so well that it qualifies as a Tear Jerker. heck, even the pilot version (Video Girl Haruno) has quite a bit of this.
His next work, I"s featured more instances of unrequited love.
In Attack on Titan, Jean immediately falls head over heels for Mikasa whose eyes are only on Eren, who has no idea that Mikasa has feelings for him and may possibly have feelings for Annie though that changed once he found out who Annie really is. Word of God confirmed that Ymir has feelings for Krista but it's unknown whether Krista feels the same. Also Krista is crushed on by several male classmates, particularly Reiner but has yet to return any feelings for them.
England MAY have got a 100-years-long and currently non-returned crush on America. The most obvious hint is the Valentines strip where England gives America some chocolates while blushing and being all embarrassed. America giving mixed signals (mocking England in one moment, claiming to be hurt because England didn't give him Valentine's chocolates in the next) doesn't exactly help matters, and neither does the fact that they're both Tsundere and * heavy* on the "tsun".
Unrequited love is the basis of the whole Belarus/Russia/Lithuania love triangle as well. Belarus likes Russia, Russia likes Lithuania (sorta), Lithuania likes Belarus, and it goes downhill from there. There's also some degree of speculation about Poland's feelings for Lithuania being not 100% platonic.
If you read a bit more on it, cases can be made for Prussia and Switzerland having unlucky Childhood Friend Romances towards Hungary and Austria, respectively.
It's also worth noting that according to the author's notes on the Greece/Japan/Turkey Love Triangle, both arrows pointing to Japan are one-sided. Even if you take the common view that Japan does reciprocate Greece's feelings or could potentially does so, that still leaves Turkey in the lurch. In fact, it's pretty hard not to see Turkey as a third wheel in the strips he gets with Japan and Greece, considering how almost all the Ship Tease for the triangle goes to Japan and Greece. Add to that the beta version of the Drama CD revealing Turkey to have been in love with Ancient Greece aka Greece's Missing Mom who he eventually killed, and his potential Foe Romance Subtext with Greece who loathes him and is sweet on Japan in at least half of all fanworks and goes "I don't completely hate you " at best in other fanworks, and well let's face it, the poor guy is a Hopeless Suitor.
Sweden at one point refers to his friend Finland as his "wife," and character notes mention that Sweden is gay, but only has feelings for Finland. Finland is freaked out by it, and tells Sweden not to joke like that. Though he both likes and looks up to Sweden, his feelings for him seem to stop at close friendship.
Black Cat has a lot of this. Kyoko, Rinslet, Saya, and Creed all fell in love with Train, though Train is mentally / emotionally immature and apparently asexual, therefore rendering all of their feelings for him unrequited. And then there's Echidna who loves Creed, but Creed is too gay for Train to care. And then there's Janus' feelings for Rinslet, but Rinslet (at least in the manga) seems to be hesitant about returning his feelings due to her crush on Train. And then there's hints that Charden might like Kyoko, who explicitly states that she would like Charden if not for Train. And then there's Eve's crush on Sven, but Sven is much more concerned with Train (being Train's Heterosexual Life Partner and all). It's all a mess.
In Brave10, Isanami and Kamanosuke form the core of a seriously Unwanted Harem for Saizo, with a few others making passes at him to no avail as well. Sasuke's implied to have a crush on Isanami in turn. Jinpachi wants Ana who is completely uninterested, and among the villains, Ishikawa Goemon one-sidedly loves Katakura Kojuro.
The majority of Code Geass characters' loves are unrequited. Kallen, Shirley, Rolo, Milly, and Kaguya are all in love with Lelouch, each in their own ways. Lelouch had a crush on Euphemia, who was falling in love with his friend Suzaku, who was falling in love with her. However, Lelouch accidentally causes Euphie to die and Suzaku went bonkers for that. Lelouch also apparently loves his full-blooded sister a bit too much, but Nunally, in addition to loving her brother just as much, has a bit of a crush on Suzaku, who still mourns for Euphemia and has lots of Foe Romance Subtext going on with Lelouch. And Milly, even though she secretly loves Lelouch, is engaged to Lloyd who is pretty much Married to the Job ( she later manages to break the engagement off, though). There's also Nina's psychotic love for Euphemia or Rivalz's own crush on Milly.
In D.Gray-Man, Bak has a huge crush on Lenalee (to the point of being a Stalker with a Crush) but she doesn't know about his feelings. Rohfa falls immediately for Allen, who is a Celibate Hero. Likewise, Road made it clear she favours Allen by planting a kiss on his lips, who only saw it as a nuisance.
In order to maintain the No Hugging, No Kissing environment of Daily Lives of High School Boys, the creator actively sinks any possible hints of romance pairings—so Hidenori thinks Literature Girl is a weirdo, the Convex Mirror Girl is an illusion, Emi is Hidenori's counsin, and Karasawa is Habara-phobic. This does not prevent others to ship, though.
Light was using Misa and Takada's affections for his own purposes. And that's all the romance between any of the main characters that is shown. Chief Yagami and Aizawa are married but their wives are almost never seen, and the flirting between Matsuda and Light's sister Sayu never goes anywhere (not that the Chief would have allowed it to).
Rem goes as far as to die out of unrequited love for Misa, despite the fact that Misa doesn't give a damn about her and it's suggested that she has thought about tricking Rem into dying for her when Rem tell her the story of Gelus, who did the same thing before Rem and for the same person.
In Digimon Adventure/Digimon Adventure 02 Tai/Taichi really likes his close childhood friend Sora, and for a while it seemed that she shared his feelings until she starts dating his best friend Matt/Yamato and marries him at the end of the series. Similarly, throughout the first half of Anime/Digimon Adventure 02 Gogglehead Davis/Daisuke crushes on Kari/Hikari but it is unrequited as she seemed to like her close friend T.K./Takeru—Davis' rival—moreso. Digimon Frontier also had it's share of unrequited love. J.P. really likes Zoe and while she seemed to value him as a friend she has a crush on Takuya instead.
In Dragon Ball Super, Trunks has a crush on Mai but she is not notoriously more interested in him, and much less after the arrival of Future Trunks. However, in the final episode of Goku Black Saga, she throws a smile at Trunks when he looks at her, which might suggest that she took interest, but later when she is sad about the departure of Future Trunks, Pilaf tells her that she still has the present Trunks, and she simply responds by giving him a judo throw, which means that she will not give in to such an idea.
Full Metal Panic!: Kaname and Tessa both love Sousuke. Sousuke has huge mental problems (including Post-Traumatic Stress Disorder and IntimacyIssues) that prevent him from returning anyone's feelings until after three whole seasons, where he finally realizes he's developing feelings for Kaname. And then there's Nami, whom Sousuke later starts developing feelings for, except she dies, so so much for that. And Lemon had feelings for Nami, but she likes Sousuke. Then there's Tsubaki, who has a crush on Kaname, and feels a great rivalry towards Sousuke, who doesn't care. And Mizuki, in turn, has a (very) unrequited crush on Tsubaki. And then there's Leonard, who is in love/lust/whatever with Kaname, who dislikes him. To add to the mix, there's Ena Saeki, who had a crush on Sousuke, who thought she was a terrorist. More weirdly, Gauron, Sousuke's Ax-Crazy psychopath Arch-Enemy, is obsessively in love with him. In a creepy, violent way. And the two twins Gauron raised, Yu Fan and Yu Lan, desperately love Gauron (and each other). Then Gates has an unhealthy pedophile obsession with the twins. This whole thing gets a lot worse when you add how a huge portion of the students at school have secret crushes / are lusting after Sousuke into the mix.
In Full Moon, Izumi loves Meroko who loves Takuto who loves Mitsuki who can't get over her dead childhood friend. Cue large helpings of Wangst (which isn't helped by Mitsuki's certain death in almost a year's time).
Both Ryuuichi and Hayato are popular among girls but they respectively are Oblivious to Love and isn't interested. In particular, Imomata and Ushimaru are interested in Ryuuichi who is more focused on caring for his little brother. Many of Ryuuichi's male classmates who have a crush on Ushimaru are envious.
Inui was pursuing Yukari who is Happily Married. Later on, Inui falls for a cute girl at the daycare - who is actually Ryuuichi in a wig. Ironically, Inui is unaware that his classmate Nekota has a crush on him.
Inui's little sister has a Precocious Crush on Hayato who is hardly aware of her existence.
Gintama mercilessly enforces this trope, mostly Played for Laughs. Kondou constantly stalks Otae, much to her annoyance. Sarutobi is madly in love with Gintoki who could care less. He also treats Tsukuyo as a friend and fellow comrade when she sees him as something more. Ayumu would do anything for Kyuubei but she's uninterested in men. Jirocho loved Otose but stepped aside when she married her husband and approved of their marriage. Matsudaira's daughter falls in love with Hijikata at first sight but he doesn't reciprocate.
The fact that Tieria Erde came to have feelings for the first Lockon Stratos (Neil Dylandy) has been pretty much accepted by fandom; the exact nature and extent are heavily debated, though romantic love is a rather viable possibility. But while Lockon did care for Tieria, even if he'd survived the first season finale, his own issues would've made very hard for him to fully reciprocate his teammate's love for him.
It is widely believed that in the chapter "Snow Mountain Syndrome", where each member of the SOS Brigade was visited in their rooms by another Brigade member, the visitor was the one that the visited was attracted to the most. Keeping this in mind, it could then be said that Kyon likes Mikuru, Mikuru likes Haruhi, and Haruhi, Yuki, and Itsukiall like Kyon. No reciprocated feelings to be found.
This is further complicated by the fact that Itsuki uses who was seen in what room to form a diagram of the number to solve the formula and let them out of the mansion and then theorizes that it was Yuki who made the fakes to give them a hint. However this may not be true as the mansion they were in was set up to provide them with everything they wanted as soon as they thought about it, such as instantly finding stuff to make sandwiches in the fridge or an ice pack that wasn't there before and right before fake!Mikuru appears in Kyon's room he was thinking about her coming in to see him. As it so happens, the diagram Itsuki drew also doesn't actually work. He drew an arabic "4" which couldn't be made given the positioning of the rooms, but a digital four (like an upside-down/flipped "h") still could have if different people had been in different rooms. Even ignoring the Snow Mountain Syndrome episode, it's heavily implied in the main series (and confirmed for the alternate universe) that Itsuki has feelings for Haruhi. Which means Itsuki likes Haruhi while Yuki and Haruhi both like Kyon.
The manga Hatsukoi Limited is essentially a massive love 20-or-so-hedron. There are all these middle schoolers, and some high schoolers, and other random people and almost all of them have an unrequited crush. Also, for much of the series, a character/unrequited love gets one chapter of screentime before being in the background for a long while; it feels really disjointed for the first few chapters. Despite this, a pretty good romantic manga.
The Heroic Legend of Arslan has quite a few. Gieve falls head over heels for Farangis who consistently brushes off his advances. Narsus is mildly annoyed that Arfrid whom he had rescued promptly declares she is in love with him. King Innocentius of Lusitania is doing everything he can, including ignoring his subjects' advice, to marry Arslan's mother Queen Tahamenay who doesn't show him any interest.
In House of the Sun,literally the only happy relationship was between Hiro's (dead) parents.
Initial D coined the term "lonely driver" referring to guys who spend most of their time working on their cars and either never get a girlfriend or have a relationship go bad on them. Takumi seems to be exempt from this, but his friends have had it happen to them (at least Itsuki had a good relationship going for a while before Kazumi dumped him for an older guy she once loved). Keisuke falls under this as well because he turns down Kyoko due to his duties as an ace of Project D. Later on, Ryosuke was revealed to have had a relationship with a girl named Kaori who also liked another guy and was eventually driven to suicide
In Kämpfer, Shizuku, Akane and Mikoto all like Natsuru, who is hopelessly in love with Kaede, who in turn lusts for Female Natsuru. Probably the only reason why the girls haven't given up on him is that they know that hell will freeze before Kaede likes Male Natsuru. It's also not helped by the fact that there's certainly some amount of Mind Control going on and Kaede is revealed to be The Big Bad. It doesn't look good for anybody
In Karakuridouji Ultimo, there's Akitsu, who loves Rune, who loves Yamato, who loves Sayama, who later turns out to love Akira, one of the Evil Doji masters. Basically, you can't get anywhere with anyone in Ultimo, because they're either gay, straight or evil.
Katekyō Hitman Reborn!. Tsuna has a big crush on Kyoko, who only seems to see him as a really good friend. Kyoko herself is a whole lot more concerned with her Hot-Blooded brother Ryouhei (though she has also expressed slight interest in Gokudera). Gokudera, in turn, is obsessively devoted to (and very heavily implied to be crushing on) Tsuna, who sees him as a good friend (but is also scared of his aggressiveness). Yamamoto wants Gokudera to "open his heart to him" and obviously wishes to further their relationship; Gokudera really dislikes Yamamoto, however, and hates how Tsuna seems more comfortable with him. Ryouhei mainly just cares about living life TO THE EXTREME (though he did have a small crush on adult I-Pin). I-Pin has a big crush on Hibari (who reminds her of her sensei). Hibari really only cares about having Foe Romance Subtext with Mukuro (and later, some with Tsuna). However, Mukuro is obsessed with having hisFoe Romance Subtext with Tsuna ("I want to possess your body" indeed). Ken and Chikusa are crazed fanboys over Mukuro, who tends to treat them like crap (save for one Pet the Dog instance). Haru loves Tsuna, who really doesn't see her that way, and constantly tries to discourage her. Hana has a crush on the future Lambo, but he barely knows her since 99% of the time he's stuck ten years in the future, leaving her to interact only with his infant self (to whom she's literally allergic). While Dr. Shamal may run after every girl who's ever passed within fifty feet of him, he has significantly more of a crush on Bianchi, who responds with a plate of Poison Cooking to the face. And then there's Bianchi herself, with an unrequited love for Reborn. Oh, and Levi's undying devotion to Xanxus is as unappreciated as Genkishi's is to Byakuran. Also Squalo has a very loud love for his boss, Xanxus. Gamma is also rather protective of Uni, and had a similar relationship with her mother Aria.
Mahou Sensei Negima! can hardly avoid this when the object of affections is a ten or elevenish year old Adorably Precocious ChildOblivious to Love who thinks of them all as students/sisters/friends. The only other love relations seen so far are Tsukuyomi → Setsuna, Asuna → Takamichi, which he feels too inferior for, Evangeline → Nagi and Natsumi → Kotarou, who is also oblivious to love. There's also the Foe Romance Subtext between Fate/Negi. Negi is apparently the only person who interests Fate enough for him to smile slightly during their battles together. He also appears very entertained when Negi starts to prove himself to be a worthy opponent, his penchant for invading Negi's personal space, or how he apparently thinks about Negi when they're not fighting sometimes. The only requited loves are Konoka/Setsuna (albeit only by implication) and Kotarou/Natsumi.
According to Word of God, Part II was supposed to have all the romance in it; no wonder things got even more complicated, with the addition of Karin being hot for Sasuke and still flipping between love and hate after he nearly killed her, Ino blushing at Sai, and the revelation that Jiraiya liked Tsunade all along. Also we have Shiho who has a major crush on Shikamaru who is Not Dating Temari. And that's not even getting into Hinata's Anguished Declaration of Love, which Naruto never responds to in the manga itself.
Then there's Kakashi's childhood, in which his childhood team had the same dynamic as his current one. Obito, Naruto's counterpart, had feelings for Rin, Sakura's counterpart, who was in love with Kakashi, who was Sasuke's counterpart. Then Obito "died", except that he didn't. However, Rin later did die, and her death is what caused Obito to become Tobi.
Asuka proclaims her love openly to Kaji, who in turn loves Misato, is not interested in an underage girl and sees Asuka like a daughter of sorts.
Gendo Ikari never moves on after the death of his wife, Yui, but this doesn't stop both Ritsuko and her mother from falling for him. He uses them professionally but never returns their affections.
Hikaru had a shy girl kind of crush on Toji and made him lunch every day, but he always remained oblivious. If he returned her feelings, he never showed it, either to her, or on-screen.
Fuyutsuki had feelings for Yui from the start, but soon enough she and Gendo were happily married.
It was implied in The End of Evangelion that Maya held feelings for Ritsuko, but, like Toji, if she did return her feelings she never showed it.
Makoto has a big crush on Misato, which she obviously doesn't ever return, and in fact sort of uses him for favors and such.
Lastly, the show's entire premise apparently sat squarely on top this trope, as its definitive ending literally hung on the truth of All Love being Unrequited. During the Tang sequence inThe End of Evangelion, the series central characters only meet their end after each one is visited by the one person that they loved the most—notice that none of these characters ever received this kind of love from these people until this point.
O Maidens in Your Savage Season: Momoko Sudo has a one-sided crush on her friend Niina Sugawara. Unfortunately for her, Sugawara develops feelings for Izumi Norimoto thus causing Momoko to become depressed over it.
One Piecethrives on this trope. There will never be any actual romance in the series, every romantic interest in the series is unrequited and Played for Laughs. Camie at the very least has a serious crush on Hatchan that he either hasn't noticed or generally ignores, Hancock is head over heels for Luffy but Oda is not shy about emphasizing the feelings are unrequited, and Sanji seems to fall for every attractive woman he meets, and the ones he's been friends with for the longest haven't come any closer to even remotely taking his flirtations seriously. ( Though this is subverted later when the mermaids, especially one named Ishilly, seem to take a shining to him, as does Princess Viola, and Charlotte Pudding.)
Peacemaker Kurogane: Saya has a thing for Tetsunosuke, Tatsunosuke is very protective of his little brother "Tetsu", Suzu was fiercely devoted to his late master Yoshida, but is now obsessed with Tetsunosuke, Tetsunosuke is the only person, other than his sister, that Susumu can relax around and show emotion towards, Okita is very fond of Tetsunosuke, Heisuke adores small cute things and frequently fawns over Tetsunosuke's cuteness, Yamanami takes a shine to Tetsunosuke, Hana tries to be a "mother figure" to Tetsunosuke To sum everything up, the entire series is rife with Ho Yay and other implications, all of it focused on Tetsunosuke and all very much unrequited, though Tetsu tries to be a equal friend to everyone.
This is the problem facing Serena during the XY arc of Pokémon. She has two guys crushing on her (recurring characters Tierno and Trevor), but she's in love with the ultimate Chaste Hero, Ash "Oblivious to Love" Ketchum. To make it even worse for her, Everyone Can See It except Mr. Oblivious.
In Princess Tutu Drosselmeyer loves this trope. To explain: Ahiru has a crush on Mytho, who is loved by both Rue and Fakir but has no feelings of his own, and later in the series Fakir develops feelings for Ahiru. The couples sort themselves out in the end.
Project A-ko: A-ko, B-ko, and their homeroom teacher Ms. Ayumi, are in love with Kei, except he only has eyes for C-ko, who can't stand his guts for inadvertently diverting A-ko's attention away from her. B-ko also has feelings for C-ko, but C-ko is soley devoted to A-ko.
Puella Magi Madoka Magica: both Sayaka and Hitomi have strong feelings for Kyousuke, who is Oblivious to Love; Hitomi is ostensibly dating him in The Movie, but he doesn't seem willing to make time for her. The additional layers come from subtext—it's heavily implied that Kyouko likes Sayaka, and Homura is downright obsessed with Madoka, but both seem to be one-way streets; Sayaka is fixated on Kyousuke, after all, and Madoka is too innocent to notice this sort of thing.
Depending on the canon, Sailor Moon and Tuxedo Mask fall into this for the first arc just with each other. In the manga, specifically, Usagi loves Tuxedo Mask and begins to love Mamoru. Mamoru loves Sailor Moon and begins to love Usagi, while also having memories of Princess Serenity. It takes the rest of the first arc for them to learn they are all the same people.
Rei loves Kaidou in the manga. She had a thing for Mamoru in the first season of the original anime and was deeply hurt when it was revealed he and Usagi were meant to be but she got over it.
Makoto loves her sempai and had a deep crush on Motoki in the first season of the original anime and the manga.
Minako loves Ace's alter ego in her manga and Alan in the original anime.
ChibiUsa has some confused feelings about Mamoru.
Setsuna may have feelings for Endymion.
Seiya loves Usagi and possibly loves Kakyuu.
Queen Beryl wanted Endymion/Mamoru in the manga, which was apparently her reason for going to the darkside.
Original anime villains Ali and En love each other but also fall for Usagi and Mamoru, respectively.
Fiore from the Sailor Moon R Movie is the Ho Yay option and loves Mamoru, or is at least VERY protective of his "friend."
Prince Diamond is obsessed with Neo Queen Serenity and, by extension, Usagi.
Emerald is infatuated with Prince Diamond and insanely jealous of Usagi.
Cooan loves Rubius, who just uses her for his own gain.
Kaorinite wants Tomoe's pants.
Rampant in Saiunkoku Monogatari: Emperor Shi Ryuuki loves Kou Shuurei, who refuses to consider marriage because she's focused on her political career. Ran Shuuei loves Shusui, who loves Kou Shouka, who loves his dead wife Shokun. Emperor Shi Senka loved a woman he couldn't marry and had six concubines he couldn't love, leading to masses of resentment from all of them. There are a few instances of couples who manage to have requited relationships—to Eigetsu and Kourin, Sa Kokujun and Sa Shunki, Tei Yuushun and Sai Rin—but they're all secondary characters and they still have to work for it.
School Rumble. The entire series revolves around a number of Love Dodecahedra, all of which are never fully resolved by the time the series has reached its end.
Almost everyone in S Cryed who is in love is unrequited or otherwise prevented—several make Heroic Sacrifices for a beloved they know is in love with someone else. One minor character has a Static Character girlfriend (who he loses and later wins back without her ever getting a single line), and Ryuhou, who does reciprocate Minori's feelings, won't act on them because of Scheris who is also in love with him. Straight Cougar practically quotes the trope name at one point in the Anime.
The manga Scum's Wish (Kuzu no Honkai) is built around this trope. Ordinary Highschool Student Hanabi is in love with her endearingly hapless teacher and childhood friend Kanai, who in turn is in love with his coworker Hot Teacher Minagawa. The other high-school protagonist, Mugi, is also in love with Minagawa. When Kanai and Minagawa start to show affections for each other, both Hanabi and Mugi realize their situations are hopeless. Bonding over their similar despair, the two pretend to start dating.note Their actual relationship is somewhere between Just Friends and Friends with Benefits, in that, while they are close friends and confidants, they have no romantic feelings for each other but engage in Sex for Solace, each pretending the other is their crush, and have strict rules on how far they can go so that they don't ruin their friendship. It is later revealed that Hanabis best friend, Ebato, has a secret lesbian crush on Hanabi, which will never be requited due to Incompatible Orientation. Meanwhile, it turns out that Minagawa is actually just leading Kanai on because she enjoys seeing the pained look on Hanabis face; thus Kanais love for her is also unrequited. On top of all that, Mugi's Childhood Friend Noriko is in love with him, and has thought of him as her "prince" since kindergarten, and Ebato's cousin Atsuya is in love with her.
Ultimately averted for Kanai and Minagawa, as Minagawa later begins to develop genuine feelings for Kanai, and accepts his marriage proposal. However, she does warn that she won't change her promiscuous behavior, and will likely cheat on him, which Kanai says he doesn't care about as long as he gets to be with her. It's also somewhat averted with Hanabi and Mugi, who also begin to develop feelings for each other, though they don't actually get together in the end.
In Slayers, the shrine maiden Sylphiel has feelings for Gourry, who in turn is: a) oblivious to them, b) too stupid to notice anyway, and c) beginning to fall for Lina, the heroine, who he's been traveling with. There is also the sorceress Eris, who loves Rezo, the Disc-One Final Boss of the first season/first several novels; he is far too obscessed with trying to cure his blindness to love another; another unrequited one for him is the anime-exclusive mechanical doll Ozzel. Meanwhile, Amelia has notable feelings for Zelgadis in the anime (not in the novels, given the No Hugging, No Kissing Rule by its author), but he either doesn't care or tries to avoid them. He does show care and concern for her at times and can talk to her casually, but he also gets fed up with her easily. Manga and game adaptations, however, have him somewhat reciporacate them. Also, in the novel, Luke loves his partner Milina, who doesn't give a flying crud. In the Hourglass of Falces manga, though, she sort of returns his feelings.
Tanukichi initially has feelings for Anna, whom he believes to be "a perfect angel", until he finds out what she's really like once she becomes fixated on him. By episode 7, he's begun to develop feelings for Ayame instead, but she only sees him as a fellow SOX member and a friend, at best.
In Stop Hibari Kun, Hibari is in love with Kohsaku, Kohsaku is in love with Rie, Rie is in love Shiina, Shiina is in love with Hibari. Needless to say, a lot of rejection occurs.
Tamako Market: Mochizou and Midori both have a crush on Tamako, who is Oblivious to Love. Dera is very openly in love with Tamako's classmate Shiori, but she never makes any indication that she even knows (and even if she did, the fact that Dera is a talking bird would probably be a bit of a turn-off). Then there's Tamako's little sister Anko, who has a crush on one of her classmates which is ultimately shot down when said classmate moves away. Furthermore there's Choi, who might have feelings for Prince Mecha... Though in The Movie, Michizou eventually confesses his feelings to Tamako, and at the very end she also responds that she loves him back. Every other ship is either sunk or given No Romantic Resolution.
I'm Gonna Be an Angel!: Noelle loves Yusuke, who loves Natsumi, who loves her deceased brother Fuyuki-meaning Raphael, who loves Mikael, who seems to be interested in Noelle in 'that' way. And it's just the beggining. There's also Muse, who loves Eros, who loves Silky, who has weird fixation on Noelle]], etc.
Tokyo Ghoul is filled with this, thanks to the emotionally-damaged cast either not realizing their feelings or outright rejecting each other for complicated reasons. Amon outright rejects Akira's advances prior to a critical battle, while Takizawa realizes his feelings for her too late to do anything about it. Hopeless Suitor Banjou accepts that he'll never be able to tell Rize how he felt about her, while the reunion between Kaneki and Touka ends in a bitter exchange of words they both regret. The finale of the original series compounds this, with Kaneki, Amon, and Takizawa all assumed dead. Touka, Tsukiyama, and Akira are left mourning them, while even Official Couple Nishiki and Kimi are forced to separate for her safety. In short, the romantic loose ends continue on into the sequel, full force.
A cute Slice of Life gag manga called Wa! by Mahoraba's Kojima Akira eats, breathes, and sleeps this trope—the founding premise of it is that each character has a crush on another character, who in turn has a crush on another character, and so on until it makes a neat loop (with the addition of those two girls who eschew romantic hijinks for Seinfeldian Conversation). Notably, though, the Love Dodecahedron in this series is more comedic than dramatic, at least so far. Chapter 9 is a summary of all the unrequited feelings of the characters up to that point. Things started to change toward the end of the series, and by the end two of the characters have managed to hook up with the person they wanted to, and one pairing possibility is pointed out by a third character, leading to the two becoming obviously closer but stay in denial.
In Vampire Knight, there is the Love Triangle of Kaname and Zero who both love Yuki who has strong feelings for both of them. Ruka always had a crush on Kaname but his eyes are only on Yuki while Kain and class president Takhiro harbors feelings for Ruka. Then there's Rido, Yuki's uncle who had unrequited feelings for Juri who is already Happily Married to Haruka but once he realized that Yuki resembled Juri, he decided to go after Yuki. Kaien also revealed to have feelings for Juri but pulled an I Want My Beloved to Be Happy instead.
One of the main theme in Your Lie in April, besides the music. Tsubaki likes Kousei, who develops a crush on Kaori, but she's interested in Watari, who is fond of her but also goes after other girls and is oblivious to her feelings. Emi meanwhile is in love with Kousei as well while Watari has displayed attraction towards her. By the end of the series, this trope becomes incredibly depressing. Tsubaki is still in love with Kousei but there's no indication of her feelings being responded to. Kaori reciprocates Kousei's feelings in a letter she wrote that Kousei didn't receive until after she passes away. In that letter, Kaori also said that she never truly interested to Watari as a lover, but in fact, Watari still has the picture of him and Kaori together in his phone, indicating that somehow, he also affected by her death. Subtlely indicating he was aware of Kaori's feeling towards Kousei and just pulling I Just Want My Beloved to Be Happy.
Kanae: I guess my wish is to be with Tohno will never come true...but I still...But I still won't be able to stop loving him. Not today, not tomorrow, not ever. I fell asleep that night crying...the only thoughts in my head being of Tohno.
Another brutal example is in Kiznaiver with the usage of a Love Dodecahedron, Nico likes Tenga, who likes Chidori, who likes Katsuhira, who likes Sonozaki. Separately, Yuta likes Maki, who has lingering feelings for Ruru, but she appreciates his gestures and as time goes by, can be seen willing to give him a chance. Hisomu is the only one not effected by this. In the finale, Katsuhira and Sonozaki get together and it is implied Chidori has moved on from Katsuhira and is starting to fall for Tenga.
The assassins Mamiya and Kurosawa knew each other when they were in school, and judging by their final conversation, Mamiya had a crush on Kurosawa and he possibly would have returned her affections if he were not gay.
The drug dealer Mischa sets her eye on Taizou when they first meet, but she gives up on him when she learns he's a Yakuza, not wanting the possible complications that might bring.
Himespetchi of Tamagotchi has a massive crush on the main character Mametchi, who is never aware that she's in love with him. This does not stop her from giving up on him by any means, however. This gets even more heart-wrenching in the 34th and 35th episodes of the Yume Kira Dream arc, which revolve around Himespetchi having to go back to her home planet at the request of her parents. Yumemitchi and Kiraritchi manage to set up one last day for Himespetchi to be with Mametchi in the latter of the two episodes, but Mametchi still doesn't get the memo and poor Himespetchi settles on going back home.
All over the place in Toilet-Bound Hanako-kun. Nene easily develops crushes on many upperclassmen, such as Teru, but they either ignore her or have outright rejected her. Kou has feelings for Nene but she only sees him as a friend. Natsuhiko declared his love for Sakura who could care less. Akane is madly in love with his childhood friend Aoi and has even asked her out several times, only to be cheerfully turned down each time.