A/N: This chapter diverges from Monsoon during the fifth chapter (not including the prologue), at the end of Madara's POV.
MADARA
"I will never leave you, Madara."
"You leave me for that bastard Senju."
"I was always bound to marry, as were you. That means little between us." Something in her eyes is searching, and Madara no longer has the energy needed to hide what she might find. "Madara—" She shifts further to her side to lie atop his chest, the same as she has done since they were children, and Madara feels the flux between them when her weight bears down, hears it in the catch in her breath and sees it in the way her eyes go wide, but Izuna does not shy from the feeling of him hard against her. Instead, she holds his eyes as his heart seizes in his chest, and relaxes, allowing her legs to fall further open across his hips.
"Izuna," he chokes through his agony, running his hands up her arms, feeling the silk bunch under his touch until he can take her face in his hands. It feels impossible, as though gravity has shifted to the space between them, pulling them nearer with unseen, unrelenting hands, and Madara's breath comes heavy and deep as Izuna moves so he might push against her firmly enough to feel how the silk between her thighs has gone wet enough to cling to her skin, wet enough to soak the cotton of his own clothes, straight through to his fevered flesh. The breath shared between them feels almost too much, but he misses it when she drops her face into the hollow of his throat and presses a soft kiss there as he sinks his fingers into her hair.
"I will always be here, with you," she swears, words hot against his skin, "no marriage would ever have changed that." She speaks to soothe, he knows, but the calm will not come. All Madara can feel, knowing Izuna feels no different to him, is great injustice that after all they've lost, they cannot even be allowed the comfort of each other's love as it exists between them. Still, no amount of mourning could see them leave each other's embrace in this moment. Madara allows himself the comfort of possession. No matter their futures, Izuna is here with him now, and her heart will always be his, her soul his, and should he wish it, he now knows her body could be his, too. It makes him feel complete in a way mostly lost to him in recent years, and the thought is too painful, the feeling too fleeting, to dwell for long.
Izuna's hands grip the side of his neck, dragging down to push past the open chest of his yukata so Madara might find bliss in the burn of her palms over his skin. If there were any need to speak between them, he would ask her to bruise, but from the harsh rhythm of her breath and the weight of her hips grinding slow against his own, he knows she understands and feels only the most inescapable guilt in allowing his own hands to wander to her nape, her thigh, leaving his own marks in turn.
Now, they have only the dim light of the lantern by which to see, but he wonders if she'll let him look in the daylight. See the marks on her skin and know his touch wasn't an imagined one. Izuna's weight splayed over his chest and hips grounds him and Madara is grateful because without it, he would surely believe himself finally driven to delusion by his desires. But above him, she is too real, perfect beyond imagining, and he knows he has not conjured her from want alone. With each roll of her hips, he rises to meet her, and Madara must feel her before he goes mad. It's too easy to run his hand up the soft skin of her thigh and feel the silk gather against his wrist, too easy to revel in the way she shivers when exposed and dip his hand between her legs to feel how his sister's body yearns to be made complete by his own.
What is not easy is to deny himself. Izuna whispers pleas in his ears, speaks promise after promise against his skin of becoming his, but he knows she cannot keep them, he cannot keep her. He cannot ruin her, though he doesn't trust himself not to and soon enough, the responsibility is taken from his hands. Izuna alleviates him of his worst burdens, as she always has.
"You have me, brother," she pants as she works open the tie of his yukata. "You will always have me." When her hands find him, neither of them can keep silent, and Madara thanks every god that might listen that their clansmen avoid their home. All he has suffered is worth it if it means knowing the sound of her want is his alone. Madara opens his mouth, still meaning to tell her they cannot, they must not, but as he goes to speak, she presses the length of him between her thighs so he might feel the slick slide of her crease as she holds him there, and what he says instead is, "You belong with me."
"I do," Izuna swears, luxuriating as he does in how well their bodies fit against one another, "I always will," she promises. When Madara feels himself catch against her, his hands fly to her hips to keep her from moving—he cannot live with ruining her, no matter how he wants to—but Izuna's feet dig themselves under his thighs to anchor herself as she tightens her legs and draws him into her body, inch by inch. Madara feels every gasp and shudder, every small sound, and the way her hands go tight where they come up to grip his wrists and keep him from pushing her away, as if he's capable of such a thing now he knows what it is to be inside of her.
She brings a hand to his chest and pushes back enough to look him in the eye as she tells him once more, "Brother, I belong to you. I am yours as you are mine, and no one else's." The curl of selfish, shameless possession around her words is what makes him feel truly known, what reminds him that they could never have been anything but this, one way or another. When she drops her head to his chest and rolls her hips over his for the first time, heat runs through him and coils tight in his belly, spurring him to grip her hips with force enough to bruise his own fingers against the sharp jut of her bones. After that, it's easy—too easy, as everything is between them—to find a rhythm that runs through both of them. To move within her is beyond what he ever truly imagined he would be allowed. It is everything, and it is not enough.
Madara pitches to the side and groans as Izuna locks her legs over his hips and allows herself to be moved with him, laid halfway on her back as she reaches up to twist her fingers into his hair as he grips her thigh with one hand, hitching it higher, tighter, and cups her head with the other, dipping to drag his tongue up the column of her throat when she lets her head tilt back in his grip. To kiss her, then, is natural, and Izuna rises to meet him as she always does, biting at his lip enough to make him bleed. The taste of blood between them only serves to further the feeling of inevitability in having her like this. They have always been the same flesh, the same blood. The hand that grips her thigh slips back behind her leg to tease at their joining and his fingers come back stained red with the blood that marks her as his before she is any other man's. When she pulls back to breathe, he licks her blood from his fingers and she takes his wrist in hand so she might do the same.
After that, they are hopelessly lost.
As he kisses down her throat, Izuna pushes her hands past his now-open yukata once more so she might claw and grip at his back and hips and feel the flex of his body against hers for herself. Madara is no stranger to desire, but to this—to her—it seems as though it should be impossible to be wanted with the same intensity with which he wants her, and yet it does not feel at all out of reach. Madara's patience slips from his grasp as he tears at the nape of her silk so he might feel her skin under his hands when he wraps his arms around her waist, holding tight so her back arches towards him. Izuna hardly cares, seems not to notice as she lets herself fall back, caught up in the rhythmic clench of her thighs and Madara finds himself pressing bruises into her waist as he watches the way her petite breasts heave with every heavy breath and meeting of their hips.
Drawn forward by unspeakable desire, he mouths open and hungry down her chest, biting at the soft swell of her breasts and rolling the peak of one under his tongue as he shudders against the feel of her hands tugging sharply at his scalp, the way she moans and shivers under him. "Izuna," he breathes her name as he kisses the hollow of her chest and struggles to hold himself steady against the encroaching tension that coils ever tighter between his hips, drawing him inward and sharpening his movements while Izuna matches every change in pace.
"I feel—" Izuna sounds lost for words, and Madara is reminded again that she has never before had a man, that she belongs, for now, to him alone, and it should come as no surprise that even in this they are in sync.
"Let go," he urges, returning to her lips and bearing down on her with his full weight, putting her flat on her back as she clings to him, "let go, and I will fall with you." She whispers his name once more against his lips, more a prayer than anything, and then Madara is given the gift of his sister's truest pleasure as she trembles and moans and falls apart under him, around him, holding fast and pulling him straight over the edge to follow as he promised. Entire body drawn tense enough to snap, Madara's breath seizes as his hips slow to a sharp, shallow grind against Izuna's, and even as her peak passes, she remains locked in his bruising grip, hands fisted in his hair and whispering of one soul, one body shared between them. What he would give for that to be true.
A/N:
Madara's terrible case of Needs To Fuck His Sister Worse Than He Needs Air disease worsens, somehow.