I never thought I'd be the guy who couldn't get it up.

At twenty-four, I was supposed to be in my prime. Fit enough from the gym, decent-looking, good job in IT that let me work remotely. Women liked me — or at least they seemed to. Drinks turned into make-outs, make-outs turned into hands under shirts, and then... nothing. My cock would start interested, half-hard from the anticipation, then decide it had better things to do. Soft. Useless. Every damn time.

The first few failures I blamed on nerves. Too much beer. Performance anxiety. But after the fifth strikeout — this time with Lauren, a gorgeous marketing girl I'd been texting for weeks — I knew it wasn't circumstantial. She was naked on my couch, straddling me, grinding against what should have been rock-solid proof of how badly I wanted her. Instead, I felt the humiliating deflation, the way her expression shifted from hungry to confused to pitying.

"I'm sorry," I muttered, pushing her off gently. "It's not you."

She laughed, but it was the kind of laugh people use when they're embarrassed for you. "Happens to everyone sometimes."

It didn't happen to me with everyone. Just everyone who wasn't... her.

Mia.

My little sister. Nineteen now, home from her first year of college for the summer. We'd always been close — shared an apartment after our parents moved to the province for Dad's job. Two bedrooms, one bathroom, thin walls. Normal sibling stuff. She walked around in tiny sleep shorts and oversized tees, hair damp from the shower, smelling like coconut conditioner. I used to tease her about it, call her a slob. Now every glimpse felt like a live wire to my groin.

I tried to ignore it at first. Told myself it was proximity. Forbidden fruit bullshit. I'd jerk off in the shower thinking about Lauren, or the barista with the lip piercing, or that porn clip I'd saved last month. Nothing. Limp as a wet sock. Then, one night after another failed date, I gave up and let my mind drift where it wanted.

Mia's laugh from the living room. The way her tank top clung when she stretched. Those long legs curled under her on the couch. The curve of her ass when she bent to pick up her phone.

Instantly hard. Painfully, throbbing hard. The kind of erection that makes your vision tunnel and your balls ache. I came in under a minute, biting my fist so she wouldn't hear.

After that, it became a pattern. I could only finish if I pictured her. Only stayed hard if the fantasy starred Mia. Real girls? Nothing. Toys? Nothing. Even the sister-themed porn I'd started secretly watching felt pale compared to the real thing living ten feet away.

I hated myself for it.

I started avoiding her. Left early for "work" even though I was remote. Stayed out late at coffee shops pretending to code. Came home after she was asleep. But the city's traffic is hell, and our place is small. You can't hide forever.

Last Friday, she caught me.

I'd had another disaster date — some girl from an app who was objectively stunning. We'd made it to her place, clothes half off, her hand on me... and again, the fade. I left, embarrassed and drove home raging at myself. Walked in at midnight to find Mia on the couch in nothing but boy shorts and a thin cami, legs tucked up, watching some Netflix drama. The living room lamp cast soft shadows over her bare thighs.

"Hey, bro," she said without looking up. "You're home early. Date bomb again?"

I grunted, headed for my room.

She paused the show. "Alex. Sit."

I froze. She only called me Alex when she was serious.

I dropped onto the armchair across from her, trying not to stare at how the fabric stretched over her chest when she leaned forward.

"What's going on with you?" she asked. "You've been ghosting me for weeks. Barely talk. Barely look at me. Did I do something?"

"No," I said too fast. "Just busy. Work. Dates. You know."

She tilted her head. "The dates aren't going well, huh?"

I shrugged.

Mia chewed her lip — that little habit she'd had since we were kids. "You used to tell me everything. Remember when you got dumped senior year and cried on my bed for an hour? I didn't judge. So... talk to me. Why do they keep failing?"

My throat went dry. I could feel the heat crawling up my neck. "It's complicated."

"Try me."

I looked away. The silence stretched. My cock twitched traitorously just from being this close to her, from the soft concern in her voice.

"I can't..." I started, then stopped. "I can't get hard for them. For anyone. Not anymore."

Her eyes widened, but she didn't laugh or recoil. She just waited.

"Like... at all?" she asked quietly.

I nodded, miserable. "Doctors say it's probably psychological. Stress or whatever. But it's not. Because..." I swallowed hard. The words felt like glass. "Because the only time it works — the only time I can even get it up anymore — is when I think about you."

The room went dead silent except for the hum of the AC.

Mia's face flushed pink. She didn't speak for a long beat. Then, very softly: "Me?"

I couldn't look at her. "Yeah. I'm fucked up, I know. I'm sorry. I'll move out if you want. Get therapy. Whatever."

She shifted, uncrossing her legs. I risked a glance — her nipples were visible through the thin top, hard little points. Was that from the cold... or something else?

"Alex," she said, voice barely above a whisper. "That's... kind of hot."

My head snapped up.

She met my eyes, cheeks still flushed, but there was something new in her gaze. Curiosity. Heat.

"I mean," she continued, "the idea that I'm the only one who can do that to you? That no other girl gets you hard anymore? Just me?" She licked her lips. "That's messed up. But... yeah. It's kind of turning me on."

My cock surged against my jeans, instant and brutal. I shifted, trying to hide it.

Mia noticed. Her eyes dropped to my lap, then back to my face. A small, wicked smile curved her mouth.

"Show me," she said.

My heart slammed against my ribs.

"What?"

"Show me," she repeated, slower. "Prove it. Prove it's only for me."

I stared at her, pulse roaring in my ears.

This was the line. Once I crossed it, there was no uncrossing.

But God help me... I was already reaching for my zipper.

My fingers fumbled with the zipper like I'd forgotten how zippers worked. Heart hammering, palms slick. Mia watched me the whole time, legs still tucked under her on the couch, that thin cami doing nothing to hide how her breathing had quickened. Her eyes were locked on my lap, wide and dark, lips parted just enough to show the tip of her tongue.

I tugged the zipper down. The sound was obscene in the quiet apartment. Then the button. Jeans parted. I hooked my thumbs into the waistband of my boxers and hesitated.

"Alex," she whispered. Not a question. A prompt.

I pushed everything down in one go. My cock sprang free, already fully hard, veins standing out, the head flushed and shiny with pre-cum. It bobbed once, heavy, pointing straight at her like it knew exactly where it wanted to be.

Mia's breath hitched. She uncrossed her legs slowly, deliberately, letting them fall open just a little. Not spreading, not yet—just enough to make the boy shorts ride up, showing the soft crease where thigh met hip.

"Jesus," she murmured. "Look at you."

I wrapped my hand around the base, more to steady myself than anything. The contact made me groan low in my throat. "See? Only you. Been like this for months. Nothing else works. Just... you."

She leaned forward, elbows on her knees, chin in her hands like she was studying something fascinating. "Months?"

"Yeah." My voice cracked. "Tried everything. Girls. Porn. My hand with every fantasy except... except the one that actually works."

Her gaze flicked up to mine. "And what fantasy is that?"

I swallowed. "You. Walking around in those tiny shorts. Bending over to grab something from the bottom shelf. Coming out of the shower with just a towel. Laughing at something stupid on your phone. You in the morning, hair messy, stealing my coffee. All of it."

Mia's cheeks flushed deeper, but she didn't look away. If anything, she seemed... pleased. Flattered in a twisted, hot way.

"And when you think about me," she said softly, "what do you do?"

"I jerk off." The words came out rough. "Fast. Hard. Picturing your mouth. Your tits. Your pussy. Imagining what you'd sound like if I ever got inside you."

She bit her lip. Hard. Then, without breaking eye contact, she reached up and slipped the thin straps of her cami down her shoulders. The fabric caught on her nipples for a second before sliding lower, baring her breasts. Small, perfect, pink nipples already tight and begging.

My hand moved on instinct—slow strokes, base to tip, spreading the slickness. "Fuck, Mia..."

"Keep going," she said. "Tell me more."

I pumped faster, eyes glued to her chest. "I think about sucking on those. Biting just enough to make you gasp. Then sliding down, spreading your legs, tasting you. Feeling how wet you'd get for your own brother."

She shivered. One hand drifted to her breast, cupping it, thumb circling the nipple. The other hand slid between her thighs, pressing against the cotton of her shorts. I could see the damp spot forming.

"Show me how hard you get," she breathed. "Show me it's really only me."

I stood up—jeans and boxers around my thighs—and stepped closer. Close enough that she could reach out if she wanted. My cock was inches from her face now, leaking steadily.

Mia's eyes darkened. She leaned in, just enough that her warm breath ghosted over the head. Not touching. Not yet. But fuck, the tease was killing me.

"Does it hurt?" she asked, almost innocently. "Being this hard for so long?"

"Yes," I hissed. "Every fucking day. Blue balls that won't quit. Jerking off three, four times thinking of you and still not satisfied."

She made a soft, sympathetic sound. Then her hand lifted—hesitant at first—and wrapped around my shaft.

I nearly buckled.

Her fingers were cool against my fever-hot skin. She squeezed gently, testing, then stroked upward, slow and deliberate. Pre-cum welled at the tip; she swiped it with her thumb and brought it to her lips, tasting.

"Oh my God," she whispered. "You taste... good."

I groaned, hips jerking forward involuntarily. "Mia—"

"Shh." She started pumping me properly now. Firm grip, twisting at the head just right. Like she'd done this before, but I knew she hadn't—not with me. "I've thought about you too, you know."

My brain short-circuited. "What?"

"Since I got back from college. Seeing you shirtless after the gym. The way your arms flex when you carry groceries. Hearing you jerk off in the shower sometimes—thin walls, remember?" She smiled, wickedly. "I used to touch myself listening to you. Pretending it was for me."

I was leaking like a faucet now. Her hand was slick, gliding easier with every stroke.

"Thought about crawling into your bed," she continued, voice husky. "Waking you up with my mouth. Letting you fuck my tits. My mouth. My pussy. Wondering if you'd be rough. If you'd call me dirty names because I'm your little sister."

"Fuck—yes." My hips rocked into her fist. "I'd be anything you want."

She sped up. "Then prove it. Come for me, Alex. Come all over your sister's hand. Show me how much you've been saving up just for me."

That did it.

My balls drew up tight. Heat exploded down my spine. I came hard—ropes of cum shooting across her wrist, her forearm, dripping onto her thigh. One spurt even hit the underside of her chin. I grunted like an animal, knees shaking, vision whiting out for a second.

Mia kept stroking through it, milking every drop, eyes wide with something like awe.

When I finally stopped pulsing, she lifted her hand—covered in me—and licked a stripe up her wrist. Slow. Deliberate.

"Tastes like you needed that," she said, smirking.

I collapsed onto the couch beside her, chest heaving. "I did. God, I really did."

She leaned over and pressed a soft kiss to my jaw. "Good. Because we're not done."

Her hand found my cock again—still half-hard, sensitive as hell—and gave it a gentle squeeze.

"Part of me wants to climb on right now," she murmured against my ear. "Feel how deep you can go. But the other part... wants to make you wait. Tease you until you're begging. Until you can't think about anyone else ever again."

I turned my head, caught her lips in a kiss—our first real one. Soft at first, then hungry. Tongues sliding, tasting myself on her.

When we broke apart, she was smiling.

"Tomorrow," she said. "When you're hard again. Because you will be. Only for me."

I nodded, already feeling the stir low in my gut.

Only for her.

To be continued...