Only Friend

"Listen - what I said before, John? I meant it. I don't have friends. I've just got one."

- Sherlock Holmes to John Watson, Sherlock

Some characters have True Companions. Some characters have social circles (however limited they may be). Alice doesn't have that. Alice has Bob. Just Bob.

There are two possible variations on the Alice character here:
 * 1) Alice is shy or a bit of a misfit, but ultimately a nice person. Bob is the only one to take the time to get to know her and realize that she's actually pretty cool.
 * 2) Alice is a Jerkass or otherwise hard to get along with. Bob is the only one willing to put up with her shenanigans.

There are also two variations on the Bob character:
 * 1) Bob is a fellow misfit who was drawn to Alice because neither of them had any other friends.
 * 2) Bob is the one with all the social skills, and may try to help Alice make more friends and/or smooth over situations where her behavior has caused problems.

While Alice-1s often go along with Bob-1s and Alice-2s with Bob-2s, they can be mixed and matched: a shy Alice might have a social Bob who tries to draw her out of her shell, while a mean Alice might have a shy Bob who's stuck with her because he's lonely or doesn't have the nerve to ditch her.

In many stories, an Only Friend doesn't stay that way for long: a nice Alice will usually have learned to make friends by the end of the story, while a mean Alice will often find Bob finally getting fed up and leaving her.

Compare with Living Emotional Crutch, which might be at play in an extreme form of this trope.

Anime and Manga

 * Jerkass Haruhi Suzumiya notes with pride in The Vanishing of Nagato Yuki-chan that only Kyon speaks to her informally. In the Suzumiya Haruhi series proper, Kyon's sister (that's all we know of her name) and Tsuruya are the only persons who are friendly towards Haruhi, without being burdened with Haruhi's secret.
 * Shy Yuki Nagato (in either series) doesn't feel comfortable going to the library without Kyon.
 * From Hana no Namae, Mizushima Kei's only friend is his editor and biggest fan, Akiyama Shinichi, though Kei tries to 'claim' that he hates Shinichi.
 * In Puella Magi Madoka Magica.
 * In Azumanga Daioh, Nyamo is Yukari's only friend.
 * In Tiger and Bunny, Barnaby pushed people away for so long that he's never had a single friend in his life before Kotetsu came along, defrosted him like no one's business, and became his Heterosexual Life Partner/Living Emotional Crutch.
 * In Legend of Galactic Heroes, it can be assumed that this trope applies to Reinhard and Reuenthal, with Kircheis and Mittermeier respectively. The latter two are sociable enough to at least be able to have friends aside from them, but Reinhard is far too busy realizing his ambition to befriend anyone but Kircheis, and Reuenthal has such a jerkassy trainwreck of a psyche that there's really only Mittermeier who would love to hang out with him.
 * Applies to Alice in Aria to a degree. Since she's extremely unsociable and cold towards anyone, it's really only Akari and Aika that she can truly call her friends. She insists that they are different from all the other girls, although this is mainly because of her warped perception of the people around her - She thinks she's disliked and envied for being talented, when in reality most people admire her.
 * In Mai-HiME, at the start of the series, Shizuru is Natsuki's only friend.
 * In High School DxD, Ophis refers to

Film

 * Jenny to Forrest Gump in their youth. And Bubba to him in the war.

Literature
"M: I am the closest thing to a friend that Sherlock Holmes is capable of having. Watson: And what's that? M: An enemy."
 * In the first Harry Potter book, Ron is Harry's only friend. Harry probably isn't Ron's only friend but since it's Harry's story we don't see Ron outside his interactions with Harry. Hermione begins the year friendless and isn't friends with Harry and Ron until midway through the book.
 * It's hinted that Ron's sister Ginny was this to Luna Lovegood.
 * Sherlock Holmes' idiosyncracies and general lack of interest in other humans except as puzzles ensures that Watson is his entire social circle. Lampshaded in Sherlock, when everyone who knows the detective is amazed he now has one friend:


 * John Carver from the I Am Not a Serial Killer trilogy is friends with another social outcast Max in order to try and avert falling into Loners Are Freaks. Despite his sociopathic nature, John makes other friends in the sequels but is so focused on his quest he pretty much still only has one friend at a time, leaving poor Max friendless.
 * In The Princess Bride, Fezzik and Inigo are each other's only friend (at least until they team up with Westley and Buttercup).

Live-Action TV
"Troy: You may have been my best friend, but we both know I was your first friend and what I know but you don't know because you have mental issues is that you’re never going to have another friend because NOBODY ELSE WILL EVER HAVE MY PATIENCE WITH YOU."
 * House has only Wilson for a friend.
 * In The Vampire Diaries, Alaric is Damon's only friend... despite the fact that they've tried to kill each other a few times.
 * Early on "In Plain Sight," Marshall and Mary proclaim each other to be this. Ultimately, it seems like their circles have expanded . . . by maybe one or two people each.
 * Thomas Lynley and Barbara Havers. He is her only true friend. Funny enough it also works in reverse - while Lynley does have one or two other close friends, he is nearly as difficult to work with as Havers is. They ultimately wind up as True Companions, via complementing each other surprisingly well, presumed betrayal, a near drowning, and more tragedy than any two people should ever have to go through.
 * Sherlock, being an adaptation of Sherlock Holmes, has this in spades between Sherlock and John, providing some of the above-mentioned Lampshading and the page quote.
 * When Troy and Abed are on the outs in Community

Theatre

 * A Running Gag in the one man play "Shylock" is that Tubal is Shylock's best friend - well, his only friend.
 * In Chess, Florence is Freddie's only friend, although by the end of the first act even she has gotten fed up with his Jerkass behavior and left him. (Which, given what we see of their interactions, is less surprising than the fact that she was with him in the first place.)

Video Games

 * In Tokimeki Memorial 2, Kaori Yae starts this way, with Kaedeko Sakura being her only friend. That's because Kaori is hugely distrustful of others due to a traumatic past experience, and Kaedeko is the only person she feels innocent, straight and honest. By the end of her storyline, when she'll solve her personal turmoils, the male protagonist will be her other close friend and lover, and she'll have made a few other friends along the way.
 * Kingdom Hearts II gives us the scene of death, where he tells Sora that Roxas was the only one he liked, and basically his only friend.
 * Though you could argue that was also a friend of, though when
 * In Ghost Trick, . This eventually changes.
 * In No More Heroes, Bishop Shidux is described as Travis Touchdown's only friend.  convinces Travis to reenter the assassin ranks in the sequel.
 * If Shepard is female and begins a romantic relationship with Garrus in Mass Effect 2, Garrus tells her she's his only friend in the galaxy. Thane admits to Shepard that s/he's the first friend he's made in twenty years. Liara suggests this when she asks Shepard for patience on Illium, saying she doesn't have enough friends left to lose him/her.
 * Due to his attitude problems, Barry Wheeler is Alan Wake's only friend, if you don't count his wife. The point is brought up several times throughout the series, with the imaginary Barry from The Writer, mentioning how pathetic it is that Wake's only real friend is his agent, and Alan admitting, through a manuscript page in American Nightmare, that, while he doesn't make friends easily, he trusts Barry completely.
 * In Katawa Shoujo, Lilly is initially Hanako's only friend, until Hanako falls in love with Hisao in her own route, and befriends Hisao and the members of the Newspaper Club in Lilly's route.

Western Animation
"Bender: Fry, of all the friends I've had... you're the first."
 * Futurama


 * Dan Vs.: Chris is Dan's only friend. Ted is occasionally mentioned, but has yet to actually appear on the show, probably because Dan is usually mad at him.
 * The first season finale of Megas XLR reveals that Non-Action Guy Jamie resents being taken on dangerous missions, and the main reason why he doesn't simply leave is because Coop's his only friend.
 * Daria: Daria and Jane (a rare combination of Alice-2 and Bob-1, respectively) are this to each other in the earlier seasons of the series. They eventually form other friendships, especially after Tom enters the mix...

Real Life

 * Many people who are autistic or have other neurological disabilities, especially if they are in their school years, will often be Alice-1s, though sometimes this is combined with the Jerkass aspects of Alice-2 and either have nice neurotypical Bob-2 friends or else act as Bob-1s to others like themselves.