This is based on a headcanon I read on tumblr, where Ino loses her mind due to overuse of the clan's jutsus. This idea wouldn't get out of my mind, so I had to write it, and here you are. I don't know if I like this, especially the ending, but here you go, and if it's terrible I apologize.

As always, not mine.

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You see, it starts small. Maybe a year after the war ends, Ino starts forgetting things. It's only little facts—where she left her hairbrush, when she's due to meet Sakura and Hinata for lunch at their favourite café, what she ate for breakfast. She doesn't think much of it; though her memory is normally flawless, she's also been more stressed than she has been in a long time—she's recently been assigned into the ANBU, and she's singlehandedly running her clan, and, of course, keeping her social life thriving. So, no, when it all begins, she doesn't realize anything is wrong with her.

Maybe if she had, she wouldn't be here now.

It keeps going on, and the things she forgets get more and more important—soon, it's no longer the location of a hairbrush or the time of a lunch date; it's missions: when they are, where she should meet with her team, the members of her team, and whether she's turned in her personal report to the Hokage. Forgetting the smaller things, she was able to brush off as being caused by stress, but this—this is something bigger. She never forgets a mission detail, not even after it's been completed and reported on. She can still tell you exact details of missions she ran with Shikamaru and Chouji and Asuma as a genin, and those were just simple chores, no big deal; these missions, the ones she's now forgetting about: they're high-level ANBU ones, assassinations and undercover and espionage, and if she forgets even one thing about some of these missions, she could get herself and whatever team she's working with killed on the spot.

(That almost happens, once. She's on an assassination mission, working with three people; while assassination is usually a solo job, their target is both trained in the shinobi arts—while his training is not as thorough as theirs, he still has the skills of a talented chuunin, and, combined with the élite jounin, and possibly formerly ANBU, bodyguards he employs, he could very well pose a challenge, even to them. They're at a fancy party—as assassination missions so often seem to take place during—and she's cozying up to their target, playing her usual part: the sweet and innocent pretty face, minor to no threat, depending on how well her weapons are hidden—usually very, very well; she's quite trained in hiding her tools—and how paranoid people are. She's talking him up, getting him comfortable with her—or at least as comfortable as possible—when her mind blanks out for five seconds and she lets something slip that a woman of the status she's faking shouldn't, couldn't know. His bodyguards are tensing and so is the target when she realizes her mistake, and oh so subtly she reaches into all five minds and edits their memory of the past ten seconds; nothing more, nothing less, no trace at all she was ever there, just like she's been trained all her life. They forget, though her target's comfort level is set far back from where she'd had him, but, while that adds extra time to their mission, at least they get through it without a fight.

It scares her, though, because she never does that, never forgets—ever.)

It only escalates from there.

She doesn't report her flub, and neither do her teammates. (The only reason for that, though, is because she gets into their minds and edits their recollection of those few seconds, too. If they remembered—which, of course, they would; they'd been watching them the entire time, even as they were turned away—they'd have told the Hokage, and he'd have ordered her in for immediate testing, because she's a Yamanaka and a Yamanaka doesn't forget things, not when they're so thoroughly trained in the art of the mind and all its aspects.) Later, as she falls deeper and deeper into her current state, she wonders if things would have turned out differently had she not hidden her mistake. Maybe, just maybe, if she hadn't she wouldn't be here now.

She looks down at her wrist, bare but for one thing—a white, plastic bracelet reading the words "Konoha Hospital".

Below that, they've listed her name, her birthdate, her shinobi ID number; everything that identifies her as Yamanaka Ino, (former) leader of the Yamanaka clan, élite ANBU agent, one of the best spies they've ever had.

And, of course, below all of that is her diagnosis: "Degrading mental functions from jutsu overuse." Then, after that, one more word, one that chills her to the bone every time she reads it.

"Irreversible."

They explained it to her like this:

During the war, she used the Yamanaka clan's jutsus a lot—and when they say that, they mean she used them far, far, far too much. Her father, one of the best at use of the clan jutsu, could use them up to twenty times within a twenty-four hour period without suffering harmful side effects.

In a sixteen-hour period, she used them sixty-five times, maybe more—they're not entirely sure of the exact count. All they know is that she grossly overused them, and as a result, her mind is slowly slipping away from her. Over the past two years, her mind has been slowly—oh, oh so slowly—sliding away from her. It wasn't in big enough chunks for her to notice until now; they think that the sudden increase in damage is from her recent assignment to the ANBU, where her mental jutsu use is high.

They say that, within the year, her mind will be gone and, in essence, she'll be a shell. Almost all the people that she knows have come by—the remaining members of the Konoha Twelve, every member of her own clan, and the majority of the Nara and Akimichi clans, along with assorted ANBU, jonin, and chuunin that she's met over her years in the ranks of Konoha. They wish her luck (she doesn't know why—she's not doing anything but waiting for her mind to disappear, and why wish her luck in that?), and tell her they'll find a cure, stop this. Sakura has been personally working on her case when she has the time, and she drops by Ino's rooms almost daily, updating her on the progress of their studies. They've kept her here in the hospital, studying her brain and testing her and trying anything they can think of. If they can slow it down even a fraction, then they buy themselves, and by extension, her, more time to at least stop the degradation where it is, if they can't reverse it.

She knows it won't work, though. She can see the brightness in Sakura's eyes, the hope in the researchers'; but she knows it's fake. She's gotten into their minds, seen the truth—it's incurable, irreversible, and within the next twelve months, she'll be gone. There will be a girl here—a girl who looks like her, with the same long blonde hair and the same bluegray eyes; a girl with all the same possessions as her; a girl with the same past as her—but it won't be her.

She'll be long, long gone.