Love is in the evening air

It was a warm august evening, it was a Friday night and we were at our cousin’s vacation house. My name is Dan, I am 15 years old and this is my experiment with my cousin.
Our parents went out with my cousin’s brother and my brother leaving us alone in the house with my 14 year old cousin.
“Goodbye, We’ll see you later!” We told them as they drove away. So with nothing to do we turned on the television. “I’m bored,” She said with a deep sigh. Her medium length brown hair swayed to the side as she stood up. I hadn’t seen her in a few years. She has grown in more ways then one. She was about 5” tall and I noticed a bra showing out from the front of her shirt. “Want to go swimming” I asked “Ok!” she said racing to her room to get changed. “Um, I’ll be down in a few minutes” I heard her shout as I walked into the bathroom next to her room to change. I took off my clothes and put on my swimsuit. And as I walked out, I saw the most beautiful sight. My cousin was wearing an incredibly cute red bikini, so I could see more of her drop dead gorgeous body. “Wow, that swim suit looks really good on you” I complimented to her. “Thanks!” she said laughing. I told her to go first since I forgot something.
As she walked down the stairs I managed to hide the hard-on I got just from seeing her. For my age I am about my normal size.