My Toxic Stepbrother

Deepening Obsession.

**Kai Voss**

I sat on the edge of my bed in the dim light of my room. The mansion was quiet now. Riley had locked herself away again after our night together. I stared at the wall that separated our rooms. My hands still remembered the way her body felt under mine. Tight. Hot. Mine.

The memory made my c**k twitch even hours later. But it was more than that. Something deeper had taken root. Riley Bennett had crawled inside my head and refused to leave.

I stood up and paced across the dark hardwood floor. My bare feet made soft sounds in the silence. The room felt too big, too empty. I stopped in front of the full-length mirror. Tattoos covered most of my chest and arms. Dark lines that told stories I never wanted to share. Stories about a mother who walked out when I was ten. Stories about nights spent wondering why I was never enough.

That was why I needed control. Always. People left. They always left. But if I owned them completely, if they belonged to me, they couldn’t disappear.

Riley was different. She fought me at every turn. Her sharp tongue, her fire, the way she looked at me with hate mixed with want. No one else challenged me like that. Most girls just spread their legs and smiled. Riley made me work for it. She made me burn.

I walked over to my desk and picked up the half-empty bottle of whiskey. I took a long drink. The burn felt good. It matched the fire in my chest.

Flashback hit me hard.

I was twelve. My mother’s suitcase by the door. She kissed my forehead and said, “Be good for your father, Kai.” Then she left. Never came back. Father told me not to cry. Voss men don’t cry. So I learned to smile instead. The cruel smirk became my armor. Power became my drug. If I controlled everything around me, nothing could hurt me again.

But Riley slipped past all of that.

I put the bottle down and moved to the window. The city lights glowed in the distance. I thought about the way she moaned my name last night. The way her nails dug into my back. The way she clung to me after we finished, even while whispering she hated me.

A dark smile pulled at my lips.

She was under my skin now. And I was under hers.

I left my room and walked down the hallway. The floorboards creaked softly under my weight. I stopped outside Riley’s door. It was closed, of course. Locked. But I could still picture her inside. Probably curled up in bed, trying to convince herself that last night was a mistake. Trying to push me away again.

I placed my palm flat against the wood. My voice came out low, almost a whisper.

“You can fight it all you want, Riley. But you’re already mine.”

I turned and continued down the hall. My mind kept replaying every moment. The first time I called her “little sis” just to piss her off. The way her leg felt under the dinner table. The rooftop. The gym. The car. The cabin. And finally, last night when I buried myself inside her and filled her up.

No one else would ever touch her again. Not that college boy at the party. Not anyone. The thought of another guy near her made my blood boil. I would break them. I would ruin them.

I went downstairs to the living room. The big windows showed the dark garden outside. I poured another drink and sat on the couch. My phone buzzed. It was Ty.

**Ty: You still coming out tonight?**

I typed back quickly.

**Kai: No. Busy.**

He replied fast.

**Ty: With your stepsister again? Bro, that’s f****d up.**

I stared at the message. Anger rose in my chest. Ty had been my friend for years. He knew my s**t. He had even been in my bed a few times when things got dark. But now he kept pushing about Riley. I didn’t like it.

I sent one more text.

**Kai: Stay out of my business, Ty.**

I tossed the phone aside. Riley was not up for discussion. Not with him. Not with anyone.

I finished my drink and stood up. The house felt different now. She had changed it. She had changed me. I used to rule this place with cold distance. Now every corner reminded me of her. The kitchen where we fought. The hallway where I pinned her. The living room where I kissed her for the first time.

I walked back upstairs. My steps were slow and quiet. I stopped again at Riley’s door. I turned the handle gently. Still locked. Good girl. She was trying to keep me out.

But she couldn’t.

I leaned my forehead against the door and closed my eyes. My voice came out soft, almost gentle, but the words carried weight.

“She’s going to be mine forever.”

I stayed there for a long minute, breathing in the silence. The obsession felt warm in my chest. It wasn’t just about f*****g her anymore. It was about keeping her. About making sure she never left like my mother did. About owning every part of her — body, mind, and soul.

I finally pushed away from the door and walked to my own room. Before I went inside, I glanced back down the hall at her closed door one last time.

Riley was asleep in there, probably dreaming about escape. But there was no escape. Not from me. Not from this house. Not from what we had become.

I stepped into my room and closed the door behind me. The cruel smirk returned to my face as I killed the lights.

She was mine now.

Whether she liked it or not.