
picture: Supernatural (Dean Winchester's single tear)
Like blood and piss, tears fall into the larger kink category of bodily fluids, and has a lot in common with those kinks. Like all kinks for bodily fluids, a kink for tears or for crying can be about a kink for release, a kink for intimacy, a kink for vulnerability, or a kink for being all messy. But tears also have their own significance, as a kind of physical proof of emotion; for many people, crying is an indicator of a strong feeling, whether positive or negative, and so this kink also has strong connections to emotion play. Your characters might be crying due to pain, stress, joy, sorrow, anguish, hatred, embarrassment, self-loathing, coercion, simple physical release, or for a host of other reasons. Someone might be told to stop crying immediately, or might be (consensually or non-consensually) gender-shamed for crying "like a girl," or might be encouraged to let it all out and cry as much as they need to, after years of holding it back. You can also imagine situations in which someone who normally can't cry is suddenly able to do so (via drugs, age regression, or bodyswap, for example), and how powerful/difficult that might be for them or for someone watching them. Alien or robot tear-substitutes happily accepted.
A kink for tears or for crying, also called dacryphilia, shows up all over in fandom (hence the front image of Dean Wincester's single tear - watching that character cry on the show Supernatural has definitely reached the status of a gleeful fetish in fandom). Getting off on watching people cry or sob/getting off on crying or sobbing can be connected to dominance/submission kinks, in which the power one person has over another can be seen in a dom's ability to push their sub to extremes: to manipulate their emotions, to cause them pain, to deny them sexual release, or to force them to endure and emotionally or physically overwhelming situation. The D/s aspect also figures in when you think about crying as a form of pure physical release that happens to people after an intense scene, especially if they've been in subspace or headspace. Crying as pure physical release, rather than an emotional one, can also happen as a reaction to pain, to altered mental states, or a range of other stimuli.
If you're interested in fanworks in which one person makes another person cry, you might also want to think about the intense intimacy that would require, and how it would intersect with trust - either the presence of trust (as in, for example, a consensual verbal humiliation scene), or the betrayal of trust (as in, for example, noncon emotional provocation). Of course, there are times in everyday life when it's not unusual for one person to help another one to get to the point of tears; the therapist's office comes to mind, with all the authority kink and medical kink that comes with it. Your characters could be patients, therapists, or people roleplaying as patients or therapists, getting off on the scene of emotional release that often happens in counseling sessions.
That moment of emotional release is also, obviously, connected to another kind of taboo, since for some people it's almost as unthinkable to let someone see you cry as it is to let someone see you take a shit. One aspect of this kink, then, is the idea that some people (especially men, and especially certain kinds of men) aren't supposed to cry, and that if they do they're debasing themselves, lowering themselves, or - of course - feminizing themselves. But for some, this lessening of emotional control (or this de-masculinization) is hot. Check out this clip from Cry Baby, which is about a guy (Johnny Depp) who can cry on command. I love the use of 60s-style falsetto singing to get at these issues surrounding masculine emotion:
[play video KB bodily secretions - CB2.avi]
Tears symbolise something real, genuine emotion, and it's obvious that Allison is thirsty for exactly that.
Like Allison, you might want to think about all the things you can do with tears once they've been cried: lick them, kiss them away, keep them in a jar and store them up to drink later. You might be interested in the physical effects of crying as well - someone getting red-eyed and unable to speak and covered in snot after a good long cry.
When someone cries in that way - with complete abandon, until their body runs out of tears and they start to hiccup and curl into a little ball - it's reminiscent of the way that children sometimes cry, innocently, loudly, without worrying about who can see them or who might judge them for it. So a kink for tears can flow very easily into an ageplay kink; your character could roleplay as a frustrated teenager with no emotional control, or a child who needs a hug from mommy/daddy/nanny/big brother/big sister, or a little baby who cries as innocently as it shits and pees, who's allowed to freak out when it's upset.
But I'm sure this only scratches the surface of a kink for tears; because there can be so much cultural baggage built up around tears, and because there are so many different ways of interacting with those ideas, there are a lot of options for this kink.
If you have more information on this kink, links to interesting resources, ideas for fandoms in which the kink might work well, or ideas for characters who you think could be into this kink, please leave a comment here! You can also feel free to post recs for stories, vids, artwork, or picspams that focus on this kink.
And if you have any questions, just comment and ask.