Tanjirou opened the door to his sister's room, checking on her for the hundredth time that day. Nezuko slowly lifted her head to look at him, her pink eyes watery and tired, but still lighting up as she saw him. Despite the pain she was feeling, she offered him a kind smile as well, just like she used to do whenever she was sick and he would help their mother take care of her.
But this wasn't truly like one of those times. Nezuko wasn't sick, she was in heat.
His pure, delicate, innocent little sister was now craving something other than blood. Her demonic instincts were starting to flourish, and she needed a mate - any mate. Tanjirou hated seeing her like this. So vulnerable, so desperate, in so much pain... and looking so perverse.
He forced himself to walk into the room, trying desperately to ignore the devious thoughts that would cross his mind so he could take care of her. Nezuko was lying on her bed, crying like a wounded animal. Her sheets were on the floor, and it looked like they had been thorned by claws. Her headboard was completely destroyed. She seemed to relax a little as he moved closer to her. He brought a hand to her forehead, and it felt like her skin was burning up. He gently helped her drink some water, then wrapped a towel that had been soaked in cold water around her neck.
Tanjirou instantly regretted it because, even though it clearly helped his little sister feel better, some of the liquid was now running down her chin and neck, slowly making it's way to her breasts, and the thin, white fabric of her clothes was now becoming transparent, allowing him to see her hard nipples.
She's your sister, he reminded himself.
Still, he couldn't help but drink in the alluring sight. His lovely, beautiful, gorgeous Nezuko, with her long, dark hair and delicate, soft, warm skin, her sweet pink eyes... wearing such a revealing dress that accentuated her curves. Lying in bed. Looking at him. Soft little whines escaping her red lips. Pressing her creamy thighs together. Needing someone. Needing anyone.
She's your sister, she's your sister.
But she needed help. She couldn't sleep or eat. What if this damaged her health? What if it made her attack a human to drink their blood? She had already destroyed half her room the previous night, losing control of her actions and of her demon strength. Who could predict what she'd do next? He had to fix this somehow.
And how long was her heat going to last? It was her third day already - how many more would there be? How long until the next? She didn't seem tempted to mate with any of the humans around her, and she would not mate with a demon - she wouldn't accept it and neither would he... but she still needed to mate with somebody. Tanjirou didn't want this idea in his mind, but it was simply the truth, and it taunted him.
"Tanjirou..." she called, bringing him back to reality.
He leaned down to talk to her, gently caressing her cheek "It will be okay, Nezuko. You just have to be strong for a little longer" he encouraged her like he would when she was little.
She grabbed his hand, kissing the back of it, then doing the same to his palm and to his fingertips. His heart melted... and then stopped beating as she sucked three of his fingers into her mouth, getting them slick with her saliva. Tanjirou watched as if in a trance, feeling his cock become hard as a rock and almost losing his mind when her demonic eyes stared back at him. Her tongue seemed to be just slightly bigger than that of a human, and her small demon teeth gently bit down on his fingers, teasing him.
Slowly, Nezuko guided his hand through her body. He could feel her pulse accelerating as he touched her neck, and couldn't help himself as moved it down to her collarbone and then to her breasts. He cupped and groped one through the fabric of her clothes, twisting the nipple and making her arch her back while she moaned.
Nezuko made him move his hand lower, touching her soft belly, and then gently placed it in between her legs, over her soaked panties.
Tanjirou panicked and tried to move away, but his sister grabbed his arm and pulled him close to her as her own hand moved to his cock, making him let out an involuntary moan. He looked into her eyes and saw nothing but lust.
But she must have noticed his fear, because she let him go with a disappointed sigh, and he ran to the door. Tanjirou made the mistake of looking back, feeling his heart sink as he saw her curling into a ball on her bed, quietly sobbing after his rejection. One last depraved thought crossed his mind.
She needs a mate. She needs someone she can trust. Who could possibly be better than her big brother?
He locked the door and slowly walked towards her. She lifted her head again, and his hands gently cupped her face, his thumbs wiping away her tears. She looked at him with those loving eyes, and he knew he was a lost man.
"I'll make you feel better" he said, leaning down and pressing his lips to hers.