He has to, doesn't he?

He squeezed his eyes shut and tried to think of anything else. Their shitty childhood. Their mom yelling. Serena sneaking him food at night. The way she used to smile at him and call him her favorite person. It helped a little, but the lust was still there, simmering under the guilt. He could still picture her on all fours, ass up, begging him to fuck her harder while she praised him as the best brother in the world.

Mason groaned quietly and leaned forward, elbows on his knees, trying to will his erection down. He couldn’t go into the bedroom right now. He couldn’t look at her. If he did, he wasn’t sure he would be able to stop himself from testing just one command. Just to see how far the obedience went.

He sat there breathing hard for a long time, fighting the darkest urges he had ever felt. The temptation was real. Painfully real. Part of him wanted to walk into that room, grab her by the hair, and make every filthy part of that fantasy come true. Pump load after load into her tight ass.

But he didn’t move. He stayed on the couch, fists clenched, cock aching, guilt eating at him.

Eventually the worst of the fantasy started to fade, leaving only a sick, heavy feeling in his stomach and a stubborn hard-on that refused to die completely.

A few minutes later Serena came back into the living room. She had put on one of his old t-shirts and a pair of loose shorts she must have found in his drawer. The t-shirt was too big on her and hung off one shoulder, but even in baggy clothes her massive breasts stretched the fabric noticeably. The shorts clung to her wide hips and thick thighs. She still looked good, too good, but at least she was covered now.

She stopped in front of him and bowed her head again. “I have dressed as you commanded, Master. Is this acceptable?”

“Yeah… it’s fine,” Mason muttered. He closed the laptop and set it aside. “Sit down.”

Serena sat on the couch across from him, knees together, back straight, hands resting on her thighs. She looked at him expectantly, waiting for the next order. Her light brown eyes were still calm and empty of the warmth he was used to seeing in his sister.

Mason leaned forward, elbows on his knees, trying to think of safe questions. “Tell me about your… training. How long have you been like this?”

“I have been in service to Alpha 7 for eight months, Master,” she answered without hesitation. “The training began during my second year at university. I was approached at a party and given my first trigger. After that the programming was built over multiple sessions.”

“Eight months…” Mason repeated quietly. That was a long time. His sister had been living with this inside her head for most of the school year and he had no idea. She had still texted him, sent him money when he needed it, asked about his classes like everything was normal. The cover personality had done its job perfectly.

“Do the other students know?” he asked carefully.

“No, Master. The cover personality maintains all normal activities. Classes, friends, studying. Only when triggered do I become **** Serena.”

Mason nodded slowly. He wanted to ask about the failsafes he was worried about, but he held back. Instead he asked, “What happens if someone who isn’t supposed to know the triggers uses them?”

“That… isn't possible master, only members of the fraternity know the triggers. I serve them until I am decommissioned” she said simply.

That meant he was stuck with her in this state for now. Unless he found the right phrase or went to Washington and confronted them directly.

He glanced at her again. Even in his baggy t-shirt he could see the heavy outline of her breasts. Every time she breathed they moved slightly under the fabric. His cock was still half-hard in his shorts. He shifted uncomfortably on the couch.

Serena noticed the movement. “Does Master require relief? I can use my mouth, my tits, or any other part of my body to serve you.”

The offer came out so casually that Mason almost choked. His face burned. “No. I don’t need that.”

“As you wish, Master.”

The silence stretched for a moment. Mason’s mind kept racing. He had the address of the frat house now. He could drive or take a cheap flight to DC. But leaving Serena alone here while she was like this felt dangerous. What if the triggers wore off wrong? What if she went back to mooing and pissing on the floor while he was gone? Or worse, what if the frat guys noticed she wasn’t responding and came looking for her?

He needed more information before he made any moves. But he had to be smart about how he got it.

“Tell me the rules,” he said finally. “What can’t you do while in this state?”

Serena tilted her head slightly. “I cannot harm myself or others unless commanded. I cannot reveal the existence of Alpha 7 to outsiders unless ordered. I must maintain cover when not actively serving. I must obey every command from my current master.”

Mason filed that away. No direct harm, but she could still be used in ways that hurt her. And she couldn’t spill secrets unless he specifically told her to.

He rubbed his temples. This was a lot to take in. His sister, his big sister, was sitting across from him like a programmable fucktoy that belonged to some secret frat. And because he had read those words out loud, she now saw him as one of her masters.

The guilt sat heavy in his chest, but so did the temptation. Every time she called him Master his cock reacted. Every time she offered her body without shame it got harder to ignore the crush he had buried for years.

He looked at her again. Serena sat perfectly still, waiting for his next words. The baggy t-shirt had slipped further off her shoulder, exposing smooth olive skin and the top curve of one heavy breast. Her light brown eyes watched him patiently.

Mason took a slow breath.

“We’re going to figure this out,” he said, more to convince himself than her. “But for now… just stay normal. Act like my sister when we’re around other people. Don’t tell anyone about any of this.”

“Yes, Master. I will obey.”

He nodded, but inside his head the questions kept piling up. How deep did the programming go? How many other girls had Alpha 7 done this to? And most importantly, how the hell was he supposed to fight an entire fraternity when his own sister was completely obedient to them?

The living room felt smaller than usual. Serena sat across from him, looking like his sister on the outside but empty on the inside, ready to do whatever he asked. Mason’s cock twitched again in his shorts as the dark thoughts crept back in.

He pushed them down for now.

But they weren’t going away.