In Death Note fanfic Fade, L gets his hands on a Death Note, containing a part of the story of Kira's rise to power. Trying to stop that from happening leads to L's own Start of Darkness as he becomes more and more similar — and arguably worse — than the killer he's trying to find.
The One I Love Is: After Asuka runs away, a depressed Shinji notes how ironic it is that he -a self-proclaimed coward and wimp- stood his ground as she -who had always been brave and indomitably stubborn- runs away.
HERZ: In chapter 2 Asuka ponders about her lifes several ironies: she had missed terribly her mother, but her mother had been always there and she had been unable to find her, open up and feel her love because Kyokos death had driven her to shut her heart; and she owed her family and her current happiness to two women she hardly considered as friends.
Asuka leaned into the kiss. She had lost much and suffered terribly, but from the ashes, she had risen anew. She had also gained so much. Things she had not dared to hope for in the past, a past that seemed like a lifetime ago. The irony of it all. Owing so much to two women she hardly considered as friends.
In Kyon: Big Damn Hero, Kyon feels guilty for kissing all the girls in the SOS Brigade through the fic because, even if he cares about them, he feels he's disrespecting them. The girls in the SOS Brigade are aiming for a polyamorous relationship with Kyon by strengthening their relationship as True Companions.
In Pokémon Master, this trope is invoked when Brock decides he'll force a mind-controlled Ash to kill Misty. He shouts "Now you'll be killed for your lover himself. How dramatic irony!"
In the Disgaea fic, Fail to the King!!, one of the antagonists is searching for the killer of his lover. Any reader who finished Disgaea 2 is well aware that Rozalin is both Zenon, the Overlord that he is hunting for revenge... and the little girl from the Snow Village that he almost gave up his quest to become a father for. He isn't.
Meta example: "I Am Unicorn" and "The First Time" make the story feel even worse than it does already.
Arguably The Worst That Could Happen. Even though the whole fic is from Kurt'sPOV and the reader technically only knows what he knows, the reader can see connections and come to conclusions that Kurt misses for a long time, mostly due to his own well-meaning cluelessness and naviety. It leaves the reader cringing through a high amount of chapters as Kurt first doesn't realize that Dave is in love with him, which in turn means that he doesn't realize that inviting his boyfriend over for the weekend to hang out with them so that Dave gets to see that healthy, gay relationships actually exist is a reallybadidea. It also takes him a really long time to realize that he's in love with Dave, which the reader has known for quite a while.
Looming Darkness has Link temporarily working with Dark Link.* really Vanitas The reader is shown all sides of the conflict, Zelda and Ciara believing that Link has gone through a FaceHeel Turn when the reader knows Link is suffering just as much as they are.
In Diaries of a Madman, Discord occasionally interjects to address the reader directly, and provides information that the main characters are unaware of. He doesn't always tell the truth, however.
Phoenix compliments Apollo and Klavier for putting their personal feelings aside and sending Kristoph, Apollo's mentor, and Daryan, Klavier's bandmate, to prison despite their close relationship. The audience knows that Apollo and Klavier framed Kristoph and Daryan.
Daryan expects Klavier to get him off murder charge that he's accused of, not knowing that Klavier is the one that framed him and fully intends to throw him under the bus.
In Mega Man Reawakened, Wily does not know Megaman is Robert at first, and neither does Tron Bonne.
The gods of dramatic irony demanded of me a snackrifice for further writing ability.
Early on in Feeling Hollow, Rukia is tricked into entering Ichigo's Mental World. She wonders out loud where his hollow is, when he's actually standing right in front of her. Rukia also comments that she half expected to run into Ichigo and the hollow fighting. Which she had. Hichigo finds the irony hilarious, even if Ichigo doesn't.
In Ancient Relics, when an thirteen-hundred-year-old immortal and incognito Merlin is in Transfiguration class at Hogwarts, the professor gives him detention for slacking off, stating, "You must grow up and live in the real world...I suggest you take the time to reflect on whether you really are as powerful as you think you are."
It's lampshaded in-universe that all of Ron's "Merlin's ___" curses are also a case of this, as he's invoking Merlin without realizing that the real guy is sitting right next to him-and very much unamused.
Shunsui and Kaien end up talking about Ichigo's possible age (which he's kept hidden), with Kaien commenting that with howhe acts he had to be at least two hundred and fifty, or two hundred, and eventually says "He can't possibly be any younger that one hundred!" The audience knows that Ichigo is actually somewhere around twenty, which would be particularly disturbing to them as typically children in Soul Society are under forty. Which would make Kaien's habit of calling Ichigo his "baby cousin" more accurate than he realizes.
In the same conversation, they also mention that though Ichigo's group is late getting back from a mission, they shouldn't worry because no one has sent a message for backup yet. What they don't know is that the leader (and the only one who could send anything) refused to do so out of pride before being knocked out in battle. The group's in fact desperate for help and barely scrapping by.
A more comedic variant is that Kaien constantly worries for his "baby cousin" Ichigo's safety, not knowing that Ichigo could kick the asses of the captains with ease.
In A Charmed LifeLight feels the safest around Ryuk, a Death God. Also Light becomes more secure in his sexuality thanks to an article that was written by L under an alias.
In the original Final Fantasy VII, Cloud was basically seen as a loser when the truth came out and Hojo didn't even recognize Cloud, even though he experimented on him for years. In the The Fifth ActHojo of this timelime thinks Cloud is his most perfect creation and scolded the other Hojo for not recognizing his own success.
In The Snow Has Stopped The Rain, Uryu thinks to himself that if he didn't know any better, he'd say Ichigo and Ganju were related because of how similar they are. Unbeknownst to him, they're cousins.
Reluctant Hero uses this quite a bit in relation to Iroh, as Yugato and Pakku respect Zuko's uncle (based on Zuko's strong loyalty to him) while fearing the Dragon of the West, unaware they are one and the same. Yugato also wonders if Iroh would be a good candidate for the Order of the White Lotus, of which he is already a member.
When the Avatar's temples are triggered, the Fire Sages think they have to find a baby or toddler as successor to the mantle. The current Avatar is actually sixteen years old and activated the temples because he entered the Avatar State rather than being born.
In Just Before The Dawn, the narrative regularly switches around between characters, resulting in the reader being far more informed than the cast at several points.
In Perfect Words, Gabriel wants to make a good impression on his crush, so he delays and delays talking to him, trying to think of a romantic way to introduce himself. He ends up blurting something out while asleep in the hospital, embarrassing himself more than if he'd simply said "Hello".
Edward hated Roy for killing his mother's family and village in Ishval and wanted to see him dead for it. Turns out Roy hates himself for Ishval as much as they do and would have let Edward kill him to make up for what he did.
Edward and Alphonse were terrified of Roy and Riza, knowing of their reputation in Ishval and feared that if their Ishvalan heritage came out that they would kill them without question. Roy and Riza would never do that to them, not that they knew that.
When Lulu and Wakka join Zuke's pilgrimage in Guardian, they console themselves with the knowledge that Yuna will be safe and sound on Besaid. Naturally, Sin attacks there while they're having a fairly quiet journey.
Almost everyone in his Praetorian Guard has backstabbed Lelouch. The one person who is genuinely loyal is Suzaku, who's a time traveller making sure that he dies at the right time.
Despite Cornelia and Schneizels fretting over Euphemia and Nunnally and fearing their safety from Lelouch, Euphemia and Nunnally don't want their "rescue".
Nunnally makes Suzaku promise to protect Lelouch when he knows that he has to let Lelouch die to ensure the timeline. Then Suzaku lets Nunnally think that he failed despite saving Lelouch's life so the timeline would remain in tact.
In One Year, Yu Narukami gets confession from his old friend, Sakura, and since he's in a relationship with Yukiko already, he decides to refuse her. The next chapter is from the POV of the confessor, who is nervous about how things will go and oblivious to Yu being in a relationship.
Code Geass Colorless Memories In Chapter 11, Suzaku is talking with Lloyd and they bring up Rai, to whom Lloyd had offered a place in his unit. However, Rai turns it down as he had joined the Black Knights partly because of Kallen of whom Suzaku knew the two hung out with each other a lot and says to these lines in response.
Suzaku: Well, you see... there's this girl that Rai hangs out with at school. If he were to join the military, though, I fear he won't be able to see her that much anymore. I would hate for them to be separated because of something that I did. Cecile:"So is this person his girlfriend or something? Suzaku: Well they never made any official statement or anything, but I think it's heading in that direction. I believe he would be safer with her than with me anyways."
Just before his trial by combat, Baelish smirks when remembering Brandon Stark's death in the latter's father's "trial by combat" against Aerys the Mad's champion — fire. Probably what was in Jon Arryn's mind when he got Littlefinger to wear heavy armor before handing him a heavy axe and sending him against his champion — the sea.
Upon meeting Gendry, Robert wonders why Joffrey had to look so much like a Lannister. The readers obviously know why.
Black Sky: Under the alias "Stefano Torreta", Theodore Nott manages to infiltrate the Vongola Famiglia in order to spy on them. Unbeknownst to him, he Harmonizes with Daniela Vongola — the former Ottava — as her Rain Guardian, meaning he's considered as a close confident and ally. For further irony, Timoteo Vongola tried for years to find another Rain Guardian for his mother, and had renunced to this endeavour just as Theo was accepted in the staff.
This trope is all over With Strings Attached thanks to the presence of the Fans, whose comments are known to the reader but not to the four, even after the four start interacting with them! Of course, the fact that the Fans lie to the four about many things doesn't help. They lie to each other, too. In fact, the whole plot is one big example of Dramatic Irony, since the four think they've been sent to C'hou, empowered, and sent on the Vasyn quest by the C'hovite gods, when it's perfectly clear to the reader that the Fans initially sent them over as part of a class experiment (which went askew) and were behind most of the empowerment and the quest. (Though the C'hovite gods did have some hand in what happened.) Actually, no, they didn't, though finding this out is a Wham Line, not Dramatic Irony.
In Friendship is Witchcraft, Sweetie Belle, who is very obviously a robot, accuses Rarity of being one because of her heartlessness and her taking acting lessons.
In this comic, Sailor Venus admits to Princess Serenity, who is upset that Venus is so formal with her, that while Serenity is her dearest friend, she can never let herself relax in the princess's presence lest she fail to protect her and that she doesn't think that will ever change. Then the final panel cuts to their Reincarnations in full Vitriolic Best Buds mode with Serena whining that Minako stole her food. This plays as a heartwarming moment as Serenity got what she wanted but also a Tear Jerker because neither of them realize just how meaningful this change is.
At one point in Trunks and Goten's Excellent Adventure, Vegeta claims that he highly doubts Trunk's "pathetic" father could be a threat to the Ginyu Force, an assertion Goten finds hilarious.
In The Best Path, Jet slowly grows to consider Zuko as one of his kids, unaware the teen is actually the Fire Prince, one of the firebenders he hates so much, thinking he's actually another victim displaced by the war.
The Lunar Rebellion: In a last-ditch attempt to keep Shadow from defecting to Celestia's cause at the beginning of the eponymous civil war, Cyclone says that if she does, the Kickers will forever be remembered as "blackguards and betrayers, lead into infamy by a madmare". In the Winningverse's present, as established well before this story was posted, the Kickers are remembered as the only clan that remained loyal during the Rebellion, and Shadow is one of Equestria's greatest heroes.
The story starts when Robert Baratheon decides to grant the eponymous island to Ned Stark's illegitimate son Jon... who's actually Rhaegar Targaryen's last surviving son and as such, entitled to the title "Prince of Dragonstone" as the rightful Crown Prince.
When Olenna rages over Margaery's betrothal to Jon, she muses her granddaughter deserves a king for a husband, not some crass Northern illegitimate son. Jon does have Northern blood since he is also the son of Lyanna Stark, but he is also acknowledged as the true King of the Seven Kingdoms since birth, so Margaery will end up a queen after all.
When Ned Stark realizes his cousin Tony is actually the Magic Knight roaming around Westeros, he wonders who serves as his Body Double to throw the Crown's suspicions out of Tony's trail - dismissing Jon Snow who's Just a Kid and as such couldn't handle such responsability. Catelyn later does the same mistake, thinking Jon is Locked Out of the Loop because a boy would be unable to keep his mouth shut if he knew his guardian is actually a masked avenger.
Ned trusts Syrio Forel to watch over Arya and bring her safe and sound at Winterfell or Iron Pointe if things get ugly in King's Landing. He's technically right, since Arya's mentor really does have her interests to heart... he only thinks these interests are very different things.
In A Song of Ice and Fire's canon, House Martell repeatedly tries and fails to arrange a wedding with House Targaryen - starting with Arianne's betrothal to Viserys falling flat because he gets himself killed then Quentyn's attempt to woo Daenerys failing because he gets himself killed. Here, Oberyn Martell decides to honour another marriage pact by offering his eldest (legitimized) daughter as a bride to Antony's heir Jon... who happens to be Rhaegar's last living child. Which means Oberyn was more successful than his brother when it came about giving a Targaryen royal a Martell spouse.
In a much darker example, Bucky sends Harry, Carol, and Jean-Paul away so that he can hunt Sabretooth without worrying about civilians or the kids getting hurt, reasoning that Jean-Paul is fast enough and the other two are tough enough to deal with whatever might come up in the meantime. Unfortunately, he hasn't bargained for Jean-Paul leaving for a bit and Maddie Pryor, one of the two most powerful psychics in history, and Badass Bookworm Dr. Sinister coming along. 44
In Prison Island Break Shadow and Silver find out they're father and son at roughly the same time, but can't bear to tell the other for fear of rejection - even though the reader knows they'd probably embrace it. Shadow starts treating Silver like a son (teaching and protecting him), while Silver starts taking on some of Shadow's stronger traits - ironically because Shadow is being kinder to him. But neither knows the other knows.
Later, Belladonna might have succeeded in killing Aurora's father Tokiomi for betraying her, but she's still unaware that Aurora didn't really want her father dead, and only followed through with the plan out of fear of being left alone.
In the Snivy Interlude, the Samurai dismissed Snivy as useless because she wasn't a Bug-type, not knowing that she had Leaf Storm and Contrary.
In the Jeanette Interlude, A.J. tells Jeanette that he always wanted to meet a Bloodliner. He doesn't know that Ash, Misty and Iris are Bloodliners.
In the Big P Pokemon Race Interlude, Lara and Hex are revealed to be Bloodliners, and the former wishes they had more Bloodliner friends, not realising they already do in Ash and Co.
In the Ritchie Gaiden, it's revealed that due to catching a fever, Ritchie was unable to attend Professor Oak's Summer Camp, missing a chance to possibly meet and even befriend Ash early on in this timeline.
Double Agent Vader gets a lot of dramatic irony out of the fact that Anakin Skywalker is Darth Vader is the highly-placed Rebel mole Ekkreth is Padme Amidala's husband is Luke and Leia's father, with very few people knowing more than one of those identities and nobody including Anakin himself knowing all of them.
After Senator Leia Organa becomes the Rebels' contact with Ekkreth, they become friends. Leia starts to see Ekkreth as a second father figure, and Ekkreth to see Leia as a daughter figure. Leia is not aware that Ekkreth is her father, and Ekkreth isn't even aware that he has a daughter. He's noticed that she has the same name he intended to give his first daughter, but is convinced it's just a coincidence.
Leia has a recurring dream of Padme, the mother she never knew in life. Once she finds out that she's Force sensitive, she correctly guesses that she's the daughter of a Jedi, but assumes because of the dream that it was her mother. During one of the dreams she remarks to Padme that she thinks Padme would have liked Ekkreth if they'd ever met.
At one point, a Rebel agent named Fulcrum gets assistance from Leia to keep Vader away from an operation Fulcrum is running. Leia and Ekkreth are amused by the irony that, unknown to Fulcrum, it's Vader himself taking on the task of distracting Vader. Unknown to any of them, there's an additional irony in the situation: Anakin never learns that Fulcrum is his old friend Ahsoka, nor Ahsoka that Leia's friend Ekkreth is her old friend Anakin.
Leia reveals to Luke that she's Force sensitive, so she can teach him what Ekkreth has taught her, and having that in common, as well as the fact that they've both been left alone after the Empire killed their families, leads them to form a close bond and adopt each other as Family of Choice, unaware that they're family by birth as well.
Luke and Leia have conversations about Luke's famous father Anakin Skywalker without being aware that he's Leia's father too, or that he's Ekkreth/Vader.
Ekkreth insists that Leia tell him nothing about the Force-sensitive pilot who destroyed the Death Star, so that there's no danger of him betraying anything to the Empire, so she doesn't tell him that the pilot's name is Luke Skywalker, which he would have immediately realized the implications of. Likewise, she doesn't tell Luke the name of her teacher in the ways of the Force, which would have triggered a similar revelation, because Luke would have recognized the name "Ekkreth" from Tatooine mythology and known that, at the very least, Ekkreth is somebody who knew his father.
Hohenheim in My Master Ed is taught alchemy by Edward, who comments on the irony of the situation, to Hohenheim's confusion. Hohenheim also mentions what a great name Alphonse is, prompting Edward to look at him funny.
One chapter flashes back to how Edward ended up 400 years in the past, and his thoughts about the ways he could save everyone, blissfully unaware of exactly how far back he truly is.
Professor Arc has several characters wonder about what life would be like if Jaune had become a student at Beacon like he intended, picturing him as the cool, popular guy everyone looked up to, not knowing he'd actually be the Butt-Monkey.
A lot of the plot of White Sheep comes from no one knowing Jaune is half-Grimm and the humanoid Grimm "Hentacle", particularly Ozpin's faction wondering what Hentacle and Salem want with Jaune, believing he must have some amazing/unusual power that's a threat to their plans. In reality, all Salem wants from Jaune is for her son to come home and give her lots of grandbabies.
Jaune and Roman both talk about how troublesome "cats" are in Service With A Smile, having no idea that they're both talking about the trouble Blake has caused for them.
In the Peggy Sue fic Relic Of The Future a time displaced Jaune Arc decides to avoid large alterations to the past so that he won't invalidate his knowledge of future event. The reader however knows that by the time he's decided this he's already prevented Summer Rose's death.
A group of human lumberjacks talk about how monsters are becoming more active and approaching closer to human villages than usual, unaware that they're being overheard by a particular monster.
While trying to cheer Heinrich up, Black Alice says that he could become a legendary hero whose name will be known by everyone. The reader already knows that this will happen from the prologue of the story.
Black Alice, after sneaking out of their inn room, hopes that Heinrich is sleeping well. The section immediately prior to this had Heinrich notice her sneaking out.
Deadly Nightshade gave Bruce Wayne a biological son in Hawthorne Isley, who very much mopes over the fact his sire is nothing but a foppish, brain-dead playboy. He outright tells this to Batman, as justification for refusing to ask his father for shelter.
Blizzard of the Red Castle has Fubuki, an orphan, looking for her parents. Akagi, it turns out, is her mother. Much yarn is made of this as the fic explores the "behind the scenes" moments in the anime, up to the reveal. Then the irony is shifted to how the satellite characters still don't know.
In Karma In Retrograde, Touya doesn't recognize Dabi at first, telling Aizawa that whoever Dabi is, he looks like the walking dead. He also scoffs at how edgy Dabi's name is. He learns a minute later that Dabi is him.
Touya:[in his head] What the fuck kind of name was Dabi? It sounded like it was made-up by someone who was trying to be edgy.
In Trusting In Faith, Nessarose thanks Glinda after she enchants her shoes so that she can walk without assistance. When Glinda tells her to be strong, Nessarose replies that she doesn't need to be anymore. Glinda's love and the Unnamed God give her strength. That was their last conversation. A few years afterwards, Nessarose was killed in a freak accident involving a house falling on her.
In To Hell and Back (Arrowverse), Iris notes that some days, it seems like Eddie is more into the Streak than he is her. Meanwhile, Eddie is complaining that some days, it seems like she's more into Barry than she is into him.
The Perfect Scry is the classical Arthur-dicovers-Merlin-actually-has-magic plot, but done in such a way that Arthur believes he was responsible for awakening Merlin's abilities. Naturally, he angsts much about it and seeks to hide the truth to everyone, including Merlin himself. Lancelot almost laughed himself sick when he heard this.
At one point, someone comments to Cyrus (who's in his disguised alias as Rebellion member Drake) that they should never trust a Ludmoore. Cyrus finds a lot of amusement in that, seeing as he is a Ludmoore, and the other person is absolutely right that they can't be trusted.
The Guardians and Chan Clan decide to keep the true nature of the girls' powers and the existence of Meridian from Section 13 for fear that their government superiors would try and take advantage of their magic and situation. Unbeknownst to them, Section 13 is secretly controlled by the Dark Hand, who know all about the other Known Worlds and the Guardians' powers, and are working towards weaponizing magic.
The Very Secret Diary: Shows up all over the place, especially early on. We know that Tom is a monster who's only using Ginny, but Ginny has no idea, and innocently loves and trusts him. As a result, a lot of Tom's lines come off as earnest, friendly, and interested to her, but sarcastic, manipulative, and sometimes downright cruel to us. For example:
In the Persona 5Peggy Sue fic series Start Again, several characters see Akechi wandering around doing his thing and worry that he's going to be a threat that needs to be dealt with. They are unaware that during the events of the first entry, The Count of Monte Cristo, Haru came back from the future, and her actions led to Akechi pulling a HeelFace Turn and never getting involved in the Conspiracy in the first place.
Tevos, Saren, and Benezia in Mass Effect: Synthesis believe that humanity is the Obliviously Evil pawns of the Reapers who will bring about the extinction of all sentient life in the galaxy and they must work with the rogue Reaper Sovereign to stop them. In reality, Sovereign is the only Reaper still attempting to continue the Cycle with the rest all devoting themselves to synthesis and determining their new purpose in the universe.
The Many Dates of Danny Fenton: Katie Kaboom had a great time on her blind date with Danny and even falls in love with him as a result. However, she is completely unaware of the fact that the only reason Danny did so many nice things for her during their date was because he did not want to risk her turning into a monster again and if anything, he seems to not want anything to do with her as a result.
The Line Is Not Broken: Naruto keeps on calling Tsunade "Granny". Unbeknownst to him, but not to her, she really is his grandmother.
When Bazett summons Scathach, Kirei tries to sneak up and kill her to take her Command Spells and Servant. Irisviel stops him by causing him to have a heart attack. Bazett and Scathach nurse him back to health, completely unaware of his murder attempt and Bazett thinking he is still her old ally.
Kirei and Gilgamesh want to use the Holy Grail to unleash Angra Mainyu, unaware that Irisviel has killed the entity.
Kirei is unaware that Zouken is dead, and thinks the old man is still lurking in the shadows planning something.
In What Might Have Been, White, Yellow an Blue gave Pink her second pearl with the intent of helping Pink become a leader. It is unlikely that they were expecting her to become the leader of a Ragtag Bunch of Misfits in direct opposition of the Empire.
In To Protect Everything, Nami (a Marine in this story) opposes the Shichibukai idea, citing how she'd never trust a pirate.