Disclaimer: I do not own Kamen Rider.

Author's Note: This is set during the final battle in All Rider vs. DaiShocker. I should really stop rewatching Decade things, but they make me feel better when the real world is being awful. The title is based off a Japanese proverb: "Fear can only be as deep as the mind allows."

Fear, As Deep as the Mind Allows

Don't!

I'm scared.

Don't!

I'm scared.

Over and over, an endless litany playing in the young man's mind, and how was she so blind to it before? How did she manage to ignore what she was doing to him, to justify in her own mind what she was doing to him? Tsukasa hurt her, yes, but she's no better than him, no different than him, and just like her brother she can't even manage to make amends.

Please don't. Don't hurt him. Don't make me hurt him.

The Rider's desperate whimpering echoes soundlessly in her ears as he continues to strive against the bonds she placed on him, attempts to claim mastery of the power she loosed. Power he's frightened of, power he doesn't want, but he'd rather face the darkest depths of his own soul than hurt Tsukasa.

Why? How? How has her brother, the older brother who abandoned her, managed to set his claws so deeply into this man? Why does he love her older brother so dearly?

Then again, he doesn't even hate her. Is certain that they can save her, is begging for her to listen to Tsukasa for her own sake as well as Tsukasa's, and she will, she will.

But Tsukikage has the stone, has ripped it from her hands, and thus she can't free the Rider right now. Soon, in just a few seconds, but not now.

Please. Don't make me kill again.

She can still hear him, though it's Tsukikage's fingers wrapped around the stone, Tsukikage urging the Ultimate Darkness closer and closer to the surface.

I'm scared. I'm so scared.

He isn't thinking that consciously. She recognizes that, finally, realizes that the terror is something deeper than the pleas. Terror she understands; terror she has lived with for over a decade, sometimes sharp and sometimes so dull she almost forgets.

Almost, but not quite, because she can't do things normal people can. Can't walk out of her house on her own, to buy groceries or play in the garden or see a friend (search for a brother). Can't go to DaiShocker on her own, but always with Tsukikage close at hand, protecting her, and why did she trust him?

Why did she take the easy way out, and how is this Rider managing to ignore his own terror in an attempt to save her brother?

Wrenching the stone free from Tsukikage's hand, she tosses it to the ground. The fragments glimmer beautifully as they fly away, and she gulps in a breath of mixed terror and anticipation. I'm sorry. You're free.

Thank you! Thank you!

(I'm scared. I'm so scared.)

She can still hear his thoughts, still see what he can see. He's shed Kuuga's form, fleeing from the terrifying power, separating himself as far as he can from the thing that he uses to define himself.

She's hurt him. She's hurt him so badly, just as badly as Tsukasa hurt her, and he's still thanking her, still worried about her and grateful to her for finally freeing him.

Tsukikage's hand connects with her cheek, wrenches her back to her own body, and she falls with a cry.

The man's mouth twists up in a disdainful snarl. "I'll deal with you later, useless wench."

He's gone, running toward the battlefield, and she curls up on the cool floor of DaiShocker's headquarters. Tears prick at her eyes. What has she done? What does she do now?

Alive. Tsukasa's alive. Tsukasa's all right.

He hurts. Every muscle in his body aches, pushed to its top capacity and beyond by Kuuga's ultimate form, and that's saying nothing of the scouring his mind and soul have taken in the last days. But Tsukasa's alive, Tsukasa's on their side, and that's enough for him to start putting the pieces of himself back together again.

If he's strong enough to do it, she can too. Sniffling, she rises from the floor, smoothing out the folds of her white dress. The color of death; the color of innocence; the color of sacrifice, and she doesn't like any of the meanings anymore.

Run, Sayo! Get out of there!

His voice stops her in her tracks, though she's used to hearing it by now. It's fuzzier already than when the stone bound them together, but still clear enough for her to hear the strength, feel the worry for her. She's in danger as long as she stays in DaiShocker's building, at the heart of the group that she's betrayed.

Just as he's in danger, Tsukikage's armored form appearing to challenge them.

(I'm scared. I'm so scared.)

Still not conscious, just a deep, dark undercurrent to his thoughts as he realizes that Tsukasa's in danger.

I'll protect him. I'll definitely protect him.

And he does, throwing himself into harm's way in a desperate bid to make sure Tsukasa survives. She cheers, covering her mouth a moment later, because drawing attention to herself is the last thing she needs to do right now. She needs to run, and trust to her brother and his strange, incomprehensible friend to take care of themselves.

(Scared. So scared. Scared.)

He's trying to ignore it, but the depth of the terror reaches out to her, threatens to drag her under, and she staggers to a halt. Both hands move to her chest, cover her rapidly beating heart as she attempts to get her breathing back under control. What's he doing? What's happening to him, to draw the terror so close?

Kuuga. He's afraid of Kuuga, but he has to use it, has to cloak himself in the darkness that his symbiote is currently reveling in and find a way to control it.

I'm sorry. I'm sorry. She's crying, tears running down her face, but she can't seem to stop it. I didn't know. I didn't mean to.

Sayo? He's confused, uncertain, his awareness of their connection having slipped to a subconscious level until she spoke again. Sayo, it's all right. I'm not mad. I'm fine. Are you safe?

No. Not yet. Closer than she has been in a long time, but she still needs to run more. Needs to get further away from this place that's claimed both her and her brother, made them into monsters.

But his terror, his self-doubt, his exhaustion is eating at her, though he's trying desperately to keep all of that away. To pretend it doesn't exist, because there are things he needs to do and he can't afford to break down right now.

Kuuga's power is wrapped around him now, but it's the dark power. The most inhuman power, the power to bring destruction, Ultimate Darkness, and he needs to control it. If someone isn't controlling it, everyone dies, and that's an outcome he can't live with.

(I'm scared.)

He charges at Tsukikage anyway. Despite everything that's happened to him, everything they've made him do and the struggle he's going through, he charges Tsukikage.

Kuuga's power surges around him, excited by the violence, desperate for release. It makes him slower than he normally would be, lets Tsukikage strike him again and again. He would be better off in one of his other forms, any other form, not having to fight against himself as well as Tsukikage, but he can't figure out how to make Kuuga respond like he wants.

She's still crying, though she's been running as well. Away from DaiShocker, and she's out of the building finally, under the bright dome of the beautiful sky. Alone, all the monsters drawn to the other side of the building by the fight, and she freezes.

Alone. Outside. Her breath catches in her throat, and her hands are shaking as she clutches at her own arms, desperate to have something to hold onto. She can't do this. She shouldn't be here. Shouldn't be out on her own. Not strong enough. Just a little chick, and she's going to be eaten out here.

You can do it, Sayo! His mental embrace is effusive, enthusiastic, though she can see right through it to the terror still dogging him. He's going to lose, and everyone's going to die, and it's going to be his fault. You're stronger than you think. You're Tsukasa's sister. You can do anything, and we'll help you. We'll definitely help you. Just keep yourself safe, and we'll meet you at your home later.

He's kneeling on the ground, hurting from a half-dozen new injuries and all the hell of the last few days. Staring up at the sky, and it doesn't frighten him. He's seen the sky of a dozen worlds, before that watched the stars in so many countries on his own world. The blue emptiness can mean loneliness, yes, but it's also the ultimate in hope. As long as you're looking at the sky, you're alive, and as long as you're alive, you can make things better.

Take control with your own hands, and make things better.

You belong to him. She doesn't know where the power comes from, the sheer determination, but she lets it flow from her mind to his to the clawing, destructive madness that she toyed with so easily before. You're Kuuga. Protector. Defender. Not what I tried to twist you into, and you belong to him.

(I'm scared. I'm so scared.)

I know. She would hug him, if they were actually near each other, if she could participate in the battle that she's helped to embroil them in. But you don't need to be. You're a good person, and you have control.

The half-consciousness that is Kuuga watches them, its raging quieted by the exchange taking place. It doesn't want to hurt Yuusuke, doesn't like what's been done to them, but it knows no other way to act. The power they've called on comes with the madness, the destructive energies too much for any human mind to withstand.

You can do it. She shoves the certainty into his mind, buries the fear and the self-doubt that she helped create in him under her own certainty. You love my brother, despite what he's done. You love me, despite what I did to you. You can definitely handle this, Yuusuke.

He does. She can't follow the mental gymnastics that occur as he completely reclaims Kuuga's power. It's too complex, too wrapped up in who he is and everything he's been through in his life for her to really understand. But she gets the gist of it, enough to understand that though he's not healed he's at least healing now, having made his peace with something so integral to his identity.

Run, Sayo. Be safe until we find you.

It's the last thing she hears from him before the link finally snaps apart. After all, there's no need for their connection anymore. Yuusuke has control of Kuuga; she's not afraid of being alone anymore.

She's still close enough to the tower to get knocked down by the wind when it collapses, to see the battle between the monster from under the castle and the giant Kamen Rider. She's not close enough to get hurt, though, and she cheers enthusiastically when the battle's finally over.

She considers running back toward them. Jumping on her brother, hugging him, apologizing for everything that's happened and hopefully getting an apology from him in turn… it's tempting. Really tempting.

But Tsukasa's going to need time to talk with his friends, and she's really not sure she's ready to see Yuusuke again right now. There are too many emotions tangled up in their relationship, both for him and for her. So she heads home, walking under a pale blue sky, seeing things more clearly than she has in a long, long time.

For the first time in a decade, she's not afraid.