Understanding Boyfriend

"Geeze, where do you freaks find these understanding guys, and where do I get one?!"

—Shelly, Wapsi Square

So you are a freak of nature, a witch, a Superhero, or a Chosen One. You are loaded with supernatural powers, and between going to work or school you have some world saving duties to attend to that need to be kept secret. And on top of that, you also need to balance it out with a love life!

But you can't tell your boyfriend about it! He'd freak out and leave you, or worse. But then, you can't keep it a secret forever, either. At some point, one of your supernatural incidents will inevitably happen exactly when you were having a romantic dinner. Or maybe your relationship has simply reached the next level, and you feel that you need to be completely honest with him.

So what now? How will he react? Well, it turns out he's perfectly okay with it (well, for the most part) and completely understands. That's right, as a reward for your sacrifices, the Powers That Be will make sure that you end up with a truly noble and loving soul who loves you for who you are and doesn't care what you are. So no worries!

This trope is a Double Standard, in that wives and girlfriends are pretty much automatically accepting of their Action Hero husband/boyfriend's actions, whereas the number of husbands/boyfriends who automatically accept that their significant other is an Action Girl are pretty thin on the ground. For the guy who is a super and needs a girlfriend, his powers are often a plus for her because it makes him more amazing. For women, finding a guy who truly doesn't have a problem with dating someone with superpowers when he's a Muggle is the bigger issue, because, well, No Guy Wants an Amazon.

Compare But Your Wings Are Beautiful, when a disguise forms part of the powers. Compare to Violently Protective Girlfriend for the Action Girl variant. Compare and contrast Nonhuman Lover Reveal, for the guy/girl who is on the other end of this trope. See also The Masquerade Will Kill Your Dating Life, which is an aversion of this trope.

Examples of Understanding Boyfriend include:

Anime and Manga

The central premise of The Secrets of Haruka Nogizaka. The titular girl is an otaku.
Ditto with My Little Sister Can't Be This Cute. Except that the guy is not a boyfriend, but the big brother... yeah.
Austria from Axis Powers Hetalia, in regards to his Victorious Childhood Friend Hungary. While he's concerned for her well-being, in the end he knows that if she wants to fight, he better lets her... since she will go One Woman Army and destroy the enemy. Considering their childhood, he knows it beforehand!
Keiko Asakura had been dumped by every single boyfriend she had when they learnt she was able to see spirits. Until the last Jerkass left her and a penniless musician with similar abilities comforted her. That guy was Mikihisa, and she would marry him.
Horribly deconstructed with Shiso and Ceres in Ayashi no Ceres. Shiso started like this, but being left helpless when he and Ceres got attacked made him very frustrated, so he asked Ceres to give him a part of her powers so he wouldn't be a burden on her. But then, said powers turned out to be too much to handle, and It Got Worse...
Shuuji in Saikano. His girlfriend is a WMD? That's ok, things will work out. Actually, they don't.
Kenta Usui from Karin, except for the boyfriend part. Until the end, that is. Comes with him doubling as Karin's crush and the Marker's Secret Keeper.
In Awkward Silence Toono Satoru's boyfriend is the only one who can read his seemingly blank and expressionless face (other than an old childhood friend of his who doesn't show up until later volumes) and understand his emotions.

Comic Books

Kong is this to Kitty Pryde in Ultimate Spider-Man, even going so far as to yell "You're welcome!" at All of the Other Reindeer for not thanking her when she saves their lives.
Back in the Golden Age, Steve Trevor was this for Wonder Woman (a remarkably progressive move for the times), and not at all threatened by the idea of getting rescued by or mooning over a woman who was twenty times stronger than him. The Silver and Bronze Age characterizations of him were...unfortunately less so, which probably led to him being deleted from continuity Post-Crisis.
In an old What If comic, Jimmy Olsen married Supergirl because of amnesia. Once she recovers and lets him know, he's totally fine with being married to Superman's cousin.

Fan Works

Gender Flipped in Ultimate Sleepwalker: The New Dreams when Alyssa Conover unwittingly learns that her boyfriend Rick Sheridan harbors a crimefighting alien warrior in his mind. At first she has a hard time dealing with it, but she actively continues supporting Rick and makes a point of trying to come to terms with Sleepwalker's presence in their lives. Once she understands what Rick and Sleepwalker have been going through, she fully accepts Sleepwalker and even starts becoming The Heart for him the way she is for Rick.

Film

In Innocent Blood, Friendly Neighborhood Vampire Marie has her understanding Cop Boyfriend Joe.
In Hancock, Ray is pretty understanding when he finds out Mary is not only the same kind of Flying Brick that Hancock is, but was also his wife.
In Turning Red, Meiling's father, Jin Lee, turned out to be this in the backstory. He was very accepting of his then-girlfriend's ability of turning into a giant red panda, to the point of understating how big the panda form of Ming was back in the day.

Literature

Elend in Brandon Sanderson's Mistborn. At least until he gets superpowers himself.
Seth in Wicked Lovely. When Aislinn tells him that she can see faeries, he has exactly one moment of "Is this a joke?" before accepting it and trying to help her with her faery situation.
In Discworld, Carrot is completely understanding about his werewolf girlfriend Angua, even the part about her not being human for one week out of four. She's actually upset that he's not upset about this at one point.

That was almost...almost one of the annoying things about him. She suspected he wouldn't mind if she shaved her head, or grew a beard. It wasn't that he wouldn't notice, he just wouldn't mind, and for some reason that was very aggravating.

In Parties and Potions by Sarah Mlynowski, Rachel is a witch and has to tell her human boyfriend Raf. It mainly escalates when she starts doing training for her witch "debutante ball" and ends up being gone whenever he wants to hangout with her. He is okay with it when he finds out, though.

Live-Action TV

The Ghost Whisperer features Jim the Understanding Husband.
Both subverted and played straight in Bewitched. The original Darrin (Dick York) was less than understanding, to the point of being downright hostile to Samantha when she used her magic. The Other Darrin (Dick Sargeant), on the other hand, tried his hardest to be understanding, the point that it was more the fault of Endora and the rest of Samantha's family that The Other Darrin didn't get along with witches.
Played with in the Sabrina the Teenage Witch TV series. Harvey does leave Sabrina when he finds out she's a witch, not out of intolerance but because she'd been using magic to mess with his life for years. He eventually does come back to her, though, and says he never had a problem with her being a witch per se.
Zack was the "gay best friend" equivalent of this in Heroes, at least until Executive Meddling got in the way.
Unless she's dating one of the undead, Buffy never got this on Buffy the Vampire Slayer. (Even Riley, who was himself a demon fighting super-soldier, had an inferiority complex due to dating a genuine superhero.) It's Willow who hit the boyfriend jackpot with Oz; upon being told the truth about the supernatural world she runs in, he replies, "Actually, it explains a lot," and just goes with the flow from there. Of course, Oz discovers he is a werewolf shortly after they begin dating, so he's more or less stuck in the supernatural world regardless, and Willow ends up having to play Understanding Girlfriend just as often.
Tyler Ford in The Middleman's unaired season finale (released as a comic)...at least, until MM pushes the Reset Button.
Allison's husband Joe on Medium believes in her powers and is understanding and accepting of them.
In Merlin, 2x09. Merlin discovers Freya turns into a bastet at night, but he isn´t afraid and still takes care of her. He even pets her cat´s head...
In the 1970s Wonder Woman TV series, especially in the first season (set in WWII), Steve Trevor comes across as completely comfortable with the fact that Diana is more physically powerful than he is, and in fact manages to work with her and make himself actively useful while giving every impression of appreciating her for who and what she is...and doesn't come across as unbelievable or weak, either.
In the TV version of The Tick, Captain Liberty and another female superhero discuss the difficulties of finding a boyfriend while picking up their dry-cleaning. Seriously subverted in this episode.
Roswell had Isobel and Jesse; she tries to send him away after he discovers she's an alien, but in the novel 'season 4', they end up together anyway.

Video Games

In Final Fantasy XIII, Serah wanders into some ruins and is made a Pulse l'Cie. Public opinion of Pulse l'Cie being... rather low, she tries to break up with Snow so he won't be associated with her should she be found out. He refuses to accept this, demands an explanation, and upon being told the truth says he will do anything to help her and proposes a few days later.
In Dragon Age II Hawke can be this if s/he's romancing Anders or Merrill. Particularly if the player character is on the friendship path.
A major part of several romances in the Mass Effect series, especially with the nonhumans, is Shepard being this about their various issues. Aside from the inherent problems of romancing, say, a drell or a quarian, the strongest is probably Jack, who only really warms up to Shepard when she realizes he cares despite, not because of, her history and nature—that is to say, he truly loves her rather than pitying her. Of course, given the people Shepard is willing to let into the Ragtag Bunch of Misfits ("Asari? Krogan? TURIANS!?") it's only to be expected.

Web Comics

Lampshaded in this Wapsi Square comic. Also the page quote.
Subverted (although this may be a retrospective way of seeing it) in Sluggy Freelance. Leo seems to be accepting of all the weird things Zoë tells about happening to her - but it turns out that was only because he thought she was lying. In the words of another jerk he hangs out with, "You've got to respect a girl who realizes romantic relationships are based on lies and goes to town with it!" As soon as Leo finds out it was all true, he feels betrayed, and they eventually break off.

Western Animation

Despite Candace's fanatical attempts to put a stop to Phineas and Ferb's projects, and her general tendency to blow minor problems out of proportion, her crush Jeremy never, ever seems to lose his cool, and they eventually end up going steady.
Danny Phantom gets this with his friends, although his tendency to "ditch" them does get on their nerves. He's also lucky enough to have an understanding sister.
Futurama: Fry doesn't seem to have a problem with Leela's big ol' eye. In fact, when Leela gets a prosthetic second eye in "The Cyber House Rules", Fry is the only one who objects, saying that he liked her better the way she was. Eventually she renounces her decision, admitting Fry was right all along.