I (22F) teased my sister’s boyfriend and got him rock hard [MF]

A few days ago I was at the apartment I share with my younger sister. She's 19 and her boyfriend Matt was over. They were watching some dumb chick flick on the couch and I decided to join them. It was hot and humid that day and I was just in tiny tight shorts and a loose t-shirt with no bra underneath. I was sweaty and the fabric clung to my chest, showing off my nipples more than I meant to. But it was my place and I didn't feel the need to dress up.

I sat on the other side of the couch, Matt in the middle and my sister cuddled up next to him. I wasn't really watching the movie but I noticed Matt shifting around a lot. I caught him staring at my chest where my t-shirt was clinging to my breasts outlining them clearly. My heart raced knowing he was flustered and I thought it'd be fun to push him a little.

About a hour into the movie my sister fell asleep leaning on the other side of the couch. I decided to make my move and tease him. I stretched, letting my shorts ride down and my t-shirt sliding up making showing my bare ass and my belly to him. I went for it and let my fingers brush his thigh, close to his crotch but not touching his dick yet. He didn't say nothing but his jeans was getting tighter and he kept clenching his jaw. He was so aroused and he was glancing to my sis to make sure she was still asleep.

I got bolder. Moved my hand closer and let it rest near his bulge. I could feel how hard he was through his jeans. His breathing got heavier and his whole body was tense.

I leaned in slight whispered "She's asleep, don't worry" into his ear.

Then I slid my hand under his waistband. Just my fingertips at first, then slowly down inside his underwear. I stroked him gently. He was thick and hard and already leaking a little. My fingers came away wet with precum. His cock pulsed under my touch and I swear I felt him twitch like he was close already.

My stomach was fluttering. I knew how wrong it was but I couldn't stop. His eyes kept jumping between me and my sister, like he wanted me so bad but was terrified to get caught. I loved it.

I just kept stroking him. Slow and soft at first, letting my fingers slide up and down the length of his cock under his briefs. He was so warm and hard and thick in my hand. I gripped him tighter and stroked him more firmly, feeling him twitch and throb with every movement. I could feel the head getting slicker with precum and used it to make each stroke smoother. He shifted his hips a little, almost like he wanted to thrust into my hand, but he was frozen in place, just letting me use him. I leaned in closer and let my wrist brush his balls while I stroked the top of his shaft, teasing him just enough to drive him crazy but not let him cum. He looked like he was holding his breath.

I finally stopped when I heard my sister shift in her sleep. I pulled my hand away like nothing happened. Matt's face was flushed red and he was trying to fix his jeans without making it obvious.

Later that night, I heard them in her room. The bed was creaking, and she was louder than usual. I guess I gave him some extra motivation. lol.

I felt a little bad, because she's my sister. But that didn't stop me from touching myself after. I didn't even wash my hands. I could still smell his dick on my fingers and I slid them inside me while I played with myself. I came hard thinking about how off-limits he is. How close I got.

The next morning, I could barely look at Matt. But deep down, I knew this wasn't over between us.