The Chaste Hero is a character, usually a teenage male, who is completelyoblivious to embarrassment of women and to romance in general. Flirtation is dismissed because he honestly doesn't get it, and pushy insistence from the Hard Drinking Party Girl or Cool Big Sis is waved off with angry annoyance. This can be a paradoxical commentary on the character's lack of "maturity," but strangely, this rule does not necessarily mean the younger male characters of the cast won't react to attractive people.
The female version is usually tomboyish and a slightly dense jock slowly being cultivated into a budding Hard Drinking Party Girl.
One bonus from this is immunity from awkwardly placed falls, gestures, and hands that plague a lot of characters — and, if it happens, no apologies for it, something the average male would be expected to do. Similarly, it pretty much allows him to interact and talk to any woman in the series, something another friend may be incapable of doing. This is especially useful if the writers are trying to avoid Shipping, simply don't want it to seem the guy is taking advantage of having many admirers, or want to set up a romantic admirer who just doesn't get that he just doesn't get it. Quite a few times, in order to allow the Chaste Hero to string along a romantic admirer without seeming like a jerk, they might say something that sounds like a love confession, only for them to continue on by saying that they also love everyone.
The Chaste Hero is very common in "juvenile" fiction, especially in the past. It gets rather annoying when he sometimes wonders why his close female friend is so nice to him.
Contrast with the Celibate Hero and Asexuality, tropes dealing with non-clueless characters that either actively shun romance or simply have no interest in it.
Compare Innocent Fanservice Girl and Ms. Fanservice. To double on the appeal, Chaste Heroes often double as Chick Magnets. See also Clueless Chick Magnet. If a seeming Chaste Hero turns out to be far more interested in sex than they appear, you've just met the Covert Pervert.
Kouji Kabuto from Mazinger Z. He was not so bad in the original manga, but in the anime series, he doesn't get when a woman is interested in him, especially if that woman is Sayaka (or Maria from UFO Robo Grendizer). If they tried to flirt, often he replied by teasing them. Given that the two of them were hot-tempered Tsunderes, you can tell how well it ended for him. Tetsuya Tsurugi from Great Mazinger was even worse, since he was so obsessively focused on fulfilling his mission (due to he thought piloting Great Mazinger was everything what he had) that if Jun tried to seduce him he didn't get it or taunted her or both (and since she had no patience for stupidty, they ended up fighting).
Judai of Yu-Gi-Oh! GX, not seen much only because there's only one female main character in his world. Of course, he's just as oblivious to the feelings of members of the same sex, anyway.
The point is driven home in one episode where he accepts a duel with a wager from an Obelisk snob, the winner being allowed to be Asuka's fiancee. Judai accepts and ultimately wins... But then it becomes clear he doesn't even know what a fiancee is.
Yuma in Yu-Gi-Oh! ZEXAL shows that he is a Chaste Hero in a pretty hilarious way. In Episode 9 he repeatedly interrupts a girl trying to confess to him during a duel only to beat her in it. Even Astral notices afterwards: "Observation #11: It seems Yuma still doesn't understand the thoughts of females."
Later, Tetsuo gets a crush on Rio and is too shy to confess. Yuma has no idea what he is trying to do.
Makoto Kousaka from Genshiken partially fits this trope; he has a girlfriend, and is hardly chaste, but is otherwise a good embodiment, oblivious to flirtation even, most of the time, his girlfriend's, as well as embarrassment.
Then again, given his demeanor no one can guess what he does during his time alone with Saki.
It's made pretty clear that he isn't a virgin and that he has slept with Saki numerous times. He does partially fit the trope in terms of his personality though.
Shungo Ninomiya, the titular character from Goshuushou Sama Ninomiya Kun ("My condolences, Mr. Ninomiya"), is a martial artist with a Hard Drinking Party Girl big sis who knows kung fu. Because of his being more or less a Chaste Hero who also knows his way around a fight, and because his being Chaste makes him semi-immune to her out-of-control magical sex appeal, she saddles him with the task of trying to "heal" a young succubus's fear of men using shock therapy... or so they say. He's also pretty much the only one unaware that his rich admirer-turned-maid friend is head over heels for him.
Ichigo Kurosaki from Bleach has various girls tease him or outright pine for him indirectly, and he doesn't bat an eye, simply calling everyone of his allies his "friends". Heck, he even cowers and partly covers his eyes whenever a girl shows any sign of advance! He's only 15 (now 16) anyway, but the way Tite Kubo draws the characters makes you wonder.
Sagara Sousuke, who doesn't recognize romance when it walks up to him and slaps him in the head with a Paper Fan of Doom. Repeatedly. He thinks that "kissing" is a synonym for "CPR", tries to "pick up women" by ambushing random women on the street, putting them in cages and holding them captive at gunpoint, and wonders what high schoolers would need condoms for, since it's unlikely they'll ever need emergency water containers.
He doesn't even understand or even remotely attempt to understand the "love" part of a "love letter." In fact, he thinks it is a death threat and the pink paper, perfume and heart signature means it's reverse psychology; obviously professional work. Though most of the death threat part was because the love letter was heavily damaged. Sousuke figured that someone put something potentially dangerous in his locker, and blew it up with high-yield explosives. Since the letter was tattered, he filled in the blanks with his twisted logic. However, without a doubt, he would've misunderstood the letter even if the letter was undamaged.
Not to mention the fact that he completely freaks out and panics every time Tessa comes on too strong (the OVA is an excellent example of this).
Neon Genesis Evangelion's Rei is the resident Emotionless Girl, so she isn't the least bit fazed when she comes out of the shower and accidentally ends up with Shinji on top of her with his hand on her breast.
She was pretty comfortable pulling a Spirit Advisor in an even more intimate position with Shinji. Understandable since Angels are sexless.
The titular character. He lives in the house with a master who has a crush on him and daily interacts with her circle of female friends who all also have crushes on him, and never notices. He also completely misinterprets all attempts to explain otherwise to him.
Hayate◊ expressly states that he falls into this trope hard.
It's been revealed that his devotion to his ex-girlfriend from age6 and his Failure Knight status to her, combined with her ingraining on him that only a self-sufficient male should pursue romance, has killed his libido. So it's a cross between this and Celibate Hero.
Strangely enough, there's no hint of this when he's staying at Hinagiku's house. He clearly has unclean thoughts of three of the members of his harem, and a negative reaction to the implication of her sister in the same position.
Hayate isn't exactly a Chaste Hero; he simply doesn't see his 13 years old Mistress and other girls of her age who are in love with him as a potential love interest because he considers them kids and he Definitely isn't a Lolicon. The situation changes when he is dealing with girls of his own age like Hinagiku, Ayumu or Maria. Probably best exemplified when Hina tries to figure out whether he likes anyone.
Hina: Do you have feelings for Ayumu? Hayate: I-I don't know... Hina: ...how about me? Hayate: Well, th-that's— Hina: How about my sister? Hayate:(instantly) No.
A use of the concept is found in Naruto, where the titular hero, despite his obvious crush on Sakura, completely misses Hinata's crush on him. This seems to be a matter of personality, as the loud and exuberant Naruto is annoyingly persistent in his pursuit of Sakura, while Hinata is so painfully shy she faints if he ever got within two feet of her. So while Naruto understands romance (sorta), he has no concept of shyness.
On the other hand, Sasuke is either a straight example of this or a Celibate Hero.
Pre Face Heel Turn at least. But Sasuke would be more likely this than Celibate Hero. The fact that one of his goals was to revive his clan and how he just tells every girl to get lost says much. Many fans even joke about how Sasuke doesn't know how babies are made.
Pre-DBZ Son Goku. He only agreed to marry Chi-Chi because he thought "marriage" was a type of food. (Their wedding night must have been an exercise in patience for Chi-Chi...)
He must have learned something from it, considering the kids they had. One's things for sure though: he sure didn't qualify for this trope anymore after getting married....
Their son, Gohan, seems to have inherited this from his father where Videl is concerned.
To his credit, he picked up on it a lot faster than Goku did, and by the end of the Buu Saga, the two are an item before marriage.
Gundam 00 has Setsuna F. Seiei, who sneaks into a young princess's bedroom at night and doesn't seem to understand the implications... Then again, Setsuna pretty much has No Social Skills and is The Stoic, which doesn't exactly help his situation.
Plus, he himself has stated twice that he shares no romantic feeling for Marina. She was just as quick with that "No". This means he actually "graduated" to Celibate Hero, since he's now aware of what romance and sex are and just doesn't act on anything romance-related. It doesn't help that he seems to view Marina more as mix of a Cool Big Sis and a Replacement Goldfish for his Missing Mom...
On the other hand, he's clearly clueless about Feldt's open feelings for him in The Movie. Even though one of his fellow Innovators was shown to have Psychic Powers! Example: Feldt is a Bridge Bunny and as such, she has no reason to personally go to the docking bay to greet Setsuna as the latter is coming back from a successful mission. Yet she does exactly that and even offers him a drink, only to get ignored in Setsuna's pre-Character Development gruff manner.Lyle even lampshades it.
Lyle: That guy can be such an idiot sometimes...
Or maybe he does know... And has no idea what to do about it. He's not a sterling example of family values, considering why his Missing Mom went missing...
Monkey D. Luffy from One Piece can't think of any reason why a naked woman would invite him into her bedroom and proclaims so. (It wasn't that, anyway.)
The latest Shrug of GodHandwavium was something to the effect that it's not that he's completely oblivious to the opposite sex, it's just that he generally doesn't pay attention to stuff like that unless he's in mixed company. Or something...
It's probably safer and more logical not to think about it too much.
He's not completely clueless to it, he's fallen to Nami's Happiness Punch.
Also he is aware (at least after the timeskip) that Hancock is in love with him and wants to marry him, he just isn't interested. Which is pretty impressive, since Hancock is considered one of the most beautiful women alive.
Oda said that he didn't want to focus on romance during the series, the characters are in love with adventure.
Ken from Science Ninja Team Gatchaman. Justified in that he spent most of his life in training to be the leader of an elite ninja team. (His Battle of the Planets counterpart Mark, though, is a Celibate Hero; while he acknowledges and admits to his feelings for Princess, he won't act on them because of duty.)
Inverted in Fairy Tail, where Lucy seems to be the only person in the entire guild with any sense of modesty. Nobody seems to understand why she would be upset when they break into her house without permission, while she's bathing.
Gray does this mostly naked on some occasions, no less. But don't worry; he took his clothes off before he got there.
Let's not forget Fairy Tail mage Natsu's lovable sense of naivety in moments any normal teenage boy would be uncomfortable, or much too comfortable, in.
Natsu's naivety may be due to Lisanna's death, it's possible he was in love with her. Though the plot elements of that haven't been explored enough.
Subverted in chapter 261 when he tries to peek on the girls in the hot springs.
Keep in mind most of the Fairy Tail members of that generation were raised together, they're all orphans and socially awkward in some way or another. It's is probably that they don't even see nudity when its each other as anything sexual.
As of the latest of the anime series, the list of girls to have shown canon feelings for him include Misty, Melody, Macey, Anabel and Angie. To say nothing of the Pokémon who have developed crushes on him....
He's been having trouble recognizing love between Pokémon too. He assumed Grovyle had a fever when Grovyle was clearly crushing on Meganium and throughout DP, he's been clueless to it all.
Early in Ash's journey through Unova, Ash captured a female Snivy with the incapacitating move Attract, which only affects Pokémon of the opposite gender. He actually uses the move against opponents, though its most likely because he recognizes it as an effective move when it hits. Meanwhile, Ash's obliviousness continues to shine through to the point that his newborn Pokémon Scraggy understands more about love than he does. Although, as of the Unova League, he does seem to have picked up on the concept of Ho Yay, at least when he's in the compromising situation...
He later doesn't understand that two Cottonees wish to mate, thinking that the male one just "wants a best buddy". This might just be the definitive showcasing of how his Characterization Marches On, as back in the first ever season of the show, Ash's Butterfree feel in love and wished to mate, and Ash was well aware of this fact.
To a lesser extent, Dawn—ironic, since she's probably the girliest of Ash's four female companions. This gives her a more "childish" feel, which is probably necessary as the last two "ten-year-old" companions seemed a lot older (in both behavior and looks).
James of Team Rocket could fall under this category as well, as the times he's shown to have fallen in love can be counted on one hand, and half the time he's under a spell (such as the Ghost on Maiden Peak episode.) The shippers will disagree, but you don't even want to start there...
Eureka from Eureka 7 is a rare female example of this at first, but she would eventually subvert it.
Brigadoon: Marin and Melan's hero, Melan Blue, is completely clueless about romance; he doesn't even know what a kiss is. Justified in that he belongs to a race of robots that apparently don't reproduce sexually (he tells Marin that he doesn't have parents), so why would he need to know about sexuality or romance?
Ichika Orimura from Infinite Stratos has this trope forced upon him, since there are at least 5 girls interested in him (with them perceiving his older sister to be a 6th rival). While he may seem incredibly dense most of the time, other times when he seems to be a little too friendly with one of the girls, the other ones get really jealous and will do what they can to stop it. Whether it's smacking him with a kendo stick while he's pinned down in bed by a naked girl grappling his arm, or nearly getting his head shot off by the girls wearing their Powered Armor suits because he tried to kiss one of them.
Fear from C3 is also a female example. She doesn't seem to clue in much about love.
Tintin. Unlike other examples, however, it is unclear whether this is a character trait or a side effect of the lack of female characters in the series.
Jughead Jones from Archie Comics. There's a reason for this, though. He hates women because he fears his heart is going to get broken a second time; the first was when his first love and childhood friend Joani Jump moved out of town. Or it was he who moved away from her.
Another reason is that he already has a girlfriend, January McAndrews, who is from the future and works with him in the Time Police and is thus kept secret.
Inverted in Pleasantville, with the entire cast being chaste and unaware of sexuality, except for the heroes.
Pirates of the Caribbean: Will Turner constantly missed his opportune moment with Elizabeth in the first film, and was so gentlemanly during their engagement that Elizabeth was practically shaking with frustration. "I'm so ready to be married...."
Though she wants desperately to change it, the socially awkward title character in Muriels Wedding is utterly clueless about sex and dating.
Lance-Constable Carrot in the Discworld novel Guards! Guards!! never got The Talk, because his dwarf foster-parents think of puberty as happening in one's fifties. Amongst other things, his innocence leads to him mishearing "bawdy house" as "boarding house" and taking lodgings in Ankh-Morpork's most popular brothel without noticing anything odd, even though his letters home make it clear one of the girls is very flagrantly propositioning him. In his next appearance (Men at Arms) he meets Angua, falls in love, and it's stated he always knew the "mechanics", even if he didn't see how they applied to him, so that meant an end to conversations like this (note that Mrs. Palm is head of the "Seamstresses'" Guild):
"What's a virgin?" he said.
"An unmarried girl," said Colon quickly
"What, like my friend Reet?" said Carrot, horrified.
"Well, no." said Colon.
"She's not married, you know. None of Mrs. Palm's girls are married."
His Citizen Of The Galaxy has the protagonist becoming friends with a woman who makes an enemy of her stepfather to help him, as well as being there for him all the time. For some reason he is mystified why she is so willing to help him. And then there's this scene earlier in the book, after the hero meets a new girl on his ship:
"Oh, just talking with Loeen. I was introducing her to n-space… and darned if she didn't catch on fast." Fritz looked judicial. "Yes, she's bright... Want to know how bright?" "Well?" "So bright that she taught in El Nido's school. Her specialty was math. Multi-dimensional geometry, in fact."
His Between Planets has the protagonist assisted by a woman who convinces her father to loan him money, despite the fact he has nothing to guarantee it. When he asks her to hold on to a ring for him (he thinks it has important secret information in it) she is startled about being given a ring and he doesn't understand why a woman would consider being given a ring something unusual. When her father finds out that the protagonist gave his daughter a ring, he questions it also, but the protagonist is still clueless about why it might be considered strange.
In Farmer In The Sky, Bill doesn't understand why Gretchen would get upset when she comes over to help him work and he immediately mentions they should also ask her sister to help. "Women are funny". When he is injured and she visits him in the hospital, "...[she] could hardly talk, which isn't like her".
Warrior Cats has Firestar in the first arc. Leafpool in Starlight might also count.
From the The Squire's Tales series by Gerald Morris, both Sir Dinadan and Beaufils. Galahad reads more as a deconstruction.
Benton Fraser of Due South has skirted this trope more than a few times; while he has been known to take an interest in women, he can be astonishingly naive about sexual matters, and he is perfectly capable of carrying on a conversation with a half-dressed exotic dancer without even thinking of breaking eye contact. (Of course, the fans have a theory about this...)
Carter in Hogan's Heroes seems absolutely clueless when it comes to women or the appeal of women, while all the other characters jump at the chance to even hang out with attractive girls. He has had one girlfriend, later his fiancee, later leaving him for a man of lower rank a year after he was captured by the Germans, but unlike the other men he only describes her in romantic terms rather than anything relating to her physical appeal.
Monk's title character, Adrian Monk is actually a widower, so he is presumed to have had a sex life once. But he's also saddled with plot-dependent OCD and phobias (which are implied to be so severe because of his wife's death). He's afraid of many things and disgusted by that which he isn't afraid of; so generally he does not consider himself available, nor is he generally considered worth approaching romantically by any female who happens to cross his path.
More to the point, Monk thinks of himself as very married, and the mere fact that his wife happens to be deceased does not make it any less so. He dates occasionally and halfheartedly, and in the end always returns to his default condition of being in love with his wife.
According to Monk while talking to his psychiatrist, the most physical his love life, even with Trudy, ever was is falling asleep holding Trudy's hand and waking up holding it.
Monk eventually came to regret not having a child with Trudy, adored a toddler after taking him in, and absolutely gushed over Molly Evans, treating her like his own simply because she was Trudy's child.
Number Six from The Prisoner takes this trope to its logical extreme. Created as a subversion of the womanizing secret agent recently popularized by James Bond, Number Six is presented with numerous female guest characters over the course of the series, and he only shows any kind of sex drive towards his fiance.
It's worth noting that the episode with Six's fiance is the episode that star/creator Patrick McGoohan is, for the most part, not in (they did a brain swap episode to get around the fact that he was in Hollywood filming Ice Station Zebra at the time). McGoohan was uncomfortable performing love scenes and tended to avoid them throughout his career.
Sheldon from The Big Bang Theory apparently has no interest in sex, but he's also shown to be oblivious to women (and men) coming on to him.
In Mr. Brain, Tsukumo is totally clueless about Kazune's advances on him (mostly due to partial brain damage caused by an accident), and keeps wondering why he's in possession of a porn magazine in the first place.
GURPS Supers: Mixed Doubles. The super heroine Justice doesn't realize how attractive she is and doesn't notice most of the compliments and passes she receives from men.
In the Book of Exalted Deeds suppliment for Dungeons & Dragons, there are many Exalted Feats that can be taken after taking the Sacred Vow Feat, all of which give a Player Character benefits if they heed the vow. Vow of Chastity is one of them. (In other words, the character gains cetain useful abilities by remaining chaste.)
This fully describes Senel Coolidge from Tales Of Legendia. There's even a point in the game where one of the female characters suddenly grabs him and pulls him into a deep, passionate kiss...twice. He, however, is completely unaffected both times.
Lloyd Irving from Tales Of Symphonia is much the same way. Observe the following exchange between him and Sheena in Flanoir:
Lloyd: "You and I are a lot alike Sheena. I think we could be great friends!"
Sheena: "Great... Friends."
Lloyd: "What, you don't wanna?"
Sheena: *Aside* "...Idiot!"
Stahn plays the trope straight... and then doesn't. He's completely oblivious to romantic infatuation he suffers from/causes towards Philia or Rutee, but when Ilene mentions she's taking him on a date, he... gets pretty expressive about the whole thing.
In the epilogue, it is made perfectly clear that at some point he got the hint.
In The Legend of Dragoon, Dart is like this at first with Shana (not to be confused with the above show), but he warms up to her by the end of the second disc.
Hilarously played by Ryusei Date in Super Robot Wars. His obliviousness on the crushes of Mai Kobayashi and Latooni Subota was apparently because he's too busy swooning over girl-shaped Humongous Mecha, as in he's more interested to those things compared to human girls. And even though Lamia is a Robot Girl, he's still not interested at her, because she's not THAT huge compared to her robot, which he swooned at too.
This is also the trait of Masaki Andoh, who is just too oblivious that he has made himself one walking harem. It got worse that in his new home La Gias, polygamy was supported, and he gets confused on who to choose, so he probably picked none to avoid much confusion. His rival Shu Shirakawa also had a walking harem following him, but he playfully ignored them... to further antagonize Masaki and adding up with their Foe Yay angle.
This is Sonic's general attitude. Particularly towards self-appointed girlfriend Amy Rose. Awkward because he's saved her a few times in the past because he thinks of her as a good friend, but she takes as evidence that he loves her.
Sonic may actually be asexual, before STH 06 (and even afterwards) Sega actually made a clear point about Sonic having no interest in girlfriends, and, amusingly, didn't think to mention the "other option." But when Sega described Sonic as "footloose and fancy free" they could have been referring to his Walking the Earth lifestyle, his laid-back nature, his "lack of interest" or the latter.
The same goes for Tails. In the comics, he has multiple girlfriends, in the games, Rouge flirting with him confuses him, and makes him think (correctly) that she has an ulterior motive.
Link of the The Legend of Zelda games has been the target of flirtation from a number of female characters, but he seems to be more taken aback than tantalized. To be fair, in most of the games he's ten years old, but he seems no less innocent as Adult Link.
The Legend of Zelda: Ocarina of Time is when it happens the most, and it's also when it's most justified. He's only ten, and even as Adult Link he only has the body of an adult. Then there's the fact that he was raised among the Kokiri. Who are kids for their entire lives. And most likely don't get involved in that sort of thing.
It's justified given the time period the games emulate. In the majority of the series, he starts out as an orphan (usually) in some tiny backwater before he heads out the grand adventure. Given such a conservative background, it's unsurprising he'd be a bit bashful and uncertain around people who take that kind of interest in him.
Hitman's titular character is kissed- on the lips- by a grateful rescuee, which results in a case of the jibblies one might get after grinding their nails over a chalkboard. Mind you, said rescuee was a kidnapped girl who had been forced into prostitution, so the 'jibblies' might just be Squick from wondering what that mouth's been doing recently. In the remade version of that mission in Hitman: Contracts, he just sneers at her grumpily. Agent 47 does seem to fit the trope, but that might have more to do with the only female in the games who isn't an unimportant civilian is his Mission Control.
Crosses over to The Movie, where Nika practically comes at him crotch-first at one point, and he goes so far as to use a sedative to get her off him. Very likely justified by the fact that 47 was bred to be a superior assassin, and a sex drive isn't very conducive to efficient killing. One reviewer noted 47's asexual proclivites and accused the movie of appealing to "adolescent male fantasies," strongly suggesting that said reveiwer has no idea what an adolescent male actually is.
Ryo Hazuki of the Shenmue series appears to not only be chaste, but asexual. Despite the very obvious advances of attractive females (Nozomi in Youkuska, and Joy in Hong Kong) stoic old Ryo can usually only muster a "Have you seen a black car?" when his love is clearly making advances. For all its sandbox and open-world play and decision-making structure, the complete lack of interaction options that make use of other characters' romantic feelings towards Ryo is quite jarring, as Chugworth Academy illustrates here.
While not actually physically chaste, sleeping with six different women throughout the storyline, Hakuoro somehow fails to realize they all love him until the very end. Oh, and the bunny princess also has a thing for him. It's most obvious with Karura, Yuzuha and Eruruw. And Urtoriy. Doriy and Guraa also express some interest, but they're more into Oboro. Seriously, that's at least nine and he only expresses vague awareness of two or three tops before the story ends.
In the Mega Man Zero series, it's questionable on how much he cares for Ciel on the "Love" scale as well (despite the latter being very obviously in love with him by the end of the series) - whether he's a Chaste Hero, a Celibate Hero, or simply too stoic to say anything out loud is left entirely ambiguous.
Despite that Mayl's is obviously hitting on him, Lan in Mega Man Battle Network is mostly clueless about Mayl's feelings for him, although time to time he's aware, and the ending of the sixth game reveals that they are married together twenty years later.
Sanada Yukimura from Sengoku Basara, a naive teenager who knows no life other than the battlefield, and is not only oblivious to any romantic feelings girls may have toward him, but also gets extremely embarrassed whenever anyone mentions such things as love, sex or relationships (which Keiji teases him about relentlessly). It doesn't help that the only mentors he has are Takeda Shingen and Sasuke.
Yukimura: "I don't understand this. Women are so complicated..."
While it never comes up in-story, the SPARTAN II's of Halo also bare mention as they quite literally are this trope, due to their sex drive being completely suppressed by their augmentations (specifically, the catalytic thyroid implant).
Terra from Final Fantasy VI is a Chaste Heroine, because she doesn't know What Is This Thing You Call Love?. The Figaro Castle guards, and even Edgar, are surprised that Terra didn't react negatively to Edgar hitting on her. She eventually learns about the feeling of love later, but she's probably still a Chaste Heroine.
In Pokémon, those Pokémon with the ability "Oblivious" is immune to being charmed.
Mario, in both video games and every other iteration. He is described as Princess Toadstool/Peach's "love interest", but they don't seem to enjoy a physical relationship. Perhaps with good reason, as at least one Nintendo-approved source describes her as still being a teenager, while he appears significantly older.
This arguably applies to Mario's younger brother Luigi as well. Granted, Mario and Luigi do blush whenever Princess Peach kisses them in gratitude for saving her.
In Assassins Creed III, the hero Connor has no known love interest or sex life despite meeting many quite attractive female characters. When one of the NPC falls in love with a woman, it takes ages for him to understand what's happening, and the first advice he offers (giving flowers to a tomboyish girl) is completely inappropriate.
Saber in Fate/stay night is completely impervious to sexual or even romantic innuendo unless it's pointed out to her. This is a popular joke in doujinshi, where she usually thinks you're talking about food.
Sinfest has Criminy. Perfectly portrayed here. Bonus points for the red demon Fucshia having a crush on him but him being oblivious to it.
25th Baam from Tower of God doesn't really realize that two beautiful princesses have at least a minor crush on him. When he returns after five years, which he presumably spent with Hwa Ryun, he at least knows how to push the buttons of a female.
In Moon Crest 24, Derek doesn't quite get why Dory laughs at him when she sees him with Lucy's clothes on. Poor guy thinks he put them on backwards.
Arguably, Hank Hill is one despite being married and in his late 40s. He has the same obliviousness to female attention, whether from his wife or any other woman. He is quite embarrassed by any display of sexuality, practically runs out screaming when he accidentally enters a porn section of a video store, and, in what is perhaps the best illustration of this side of his character, when he meets two young female nudists he winds up lecturing them on the benefits of propane heating for their summer home.
"Nobody rejects Debbie Grund!" "Well I just did!"
Another example: He was talking with a Doctor and behind him, there was a poster in the wall that displayed a women uterus and related organs, during the entire conversation Hank would try to avoid look at the thing.
He may have grown up with an older mindset about marriage and romance.
Kyle Broflovski in South Park. Apart from a crush on a girl named Rebecca in season three, he's the only one of the main boys with little to no interest in romance or girls. Then again, he IS nine...
Cartman is the anti-hero version of this trope. He seems to be more focused on making lives of others miserable and other things than romance.
Although in the "Le Petit Tourette" episode, Cartman did say he fancied and fantasized about kissing this girl named Patty Nelson.
Ace Lightning - The titular main character doesn't even know how to flirt.
Phineas from Phineas And Ferb, who remains completely oblivious to his best female friend's repeated hints that she has a crush on him. The fact that his same-age (step)brother is a borderline Covert Pervert only emphasises this.
This dialogue shows this quite nicely:
Phineas: Ferb and I are going to use a laser to carve our faces in the comet, so that when it passes over again in 73.5 years our grandchildren will see it. By the way, my parents are cooking outdoor steaks for everyone. What do you think, Isabella?
Freddy in the newest Scooby Doo series has become this trope. Ironically enough, the series cranks the historic Ship TeaseUp to Eleven but he remains oblivious to all of Daphne's advances due to his obsession with solving mysteries and planting traps.