My stepsister took my virginity

Hi, i’m mark 16 years old. A normal teen boy with the usual teen interests. I’m about 1,8m tall, weigh about 75kg, blue eyes, dark brown hair. I’m no superman, but keep myself in decent shape.
I have a stepsister, Lisa who is 18. She is tall, slim, with long light brown hair, and beautiful C cup breasts and a nice round butt. I always sneak a peek at her whenever i can get a look at her body. But never actually thought about having sex with her, until tonight that is.
We were very close, and had quickly become good friends when our parents started dating, and later married.

Our parents was going away for the weekend. Taking a romantic getaway as they usually do a couple of times a year. Leaving me and my 18 year old stepsister home alone for the weekend.

After saying goodbye to our parents, i went up to my room. It was Friday afternoon and raining, so it looked like it would be a boring evening. My stepsister came into my room without knocking. She never knocked, but i didn’t really mind. She asked if i had any plans for the weekend. I told her i didn’t have any special plans, staying home tonight, maybe see some friends tomorrow and Sunday. She told me she was going out with her friend Tina that night. They planned to go to a party and would probably be home late. And she asked if i was OK with being alone for the night. I told her it was no problem and to have fun. Is a bit of a party animal, and liked going out on weekends. I knew she wasn’t a virgin, but she was no slut either. Although i knew she played around with Tina sometimes, but they were never more than friends with benefits.

After Lisa left for her party i relaxed at home. Fixed myself some food, watched a movie, and played on my computer.