You refuse

You look up at your sisters daunting cock eagerly waiting to slam itself into you but with a act of not wanting to do this again you stand up and with one word say this

“No” you said looking at her, she was a bit taller then you and had the breasts to match a girl at her height (she’s 6’5). Your sister looks at you with a raised eye brow and sighs as she knew this would happen eventually but quickly came up with a plan

“Alright I won’t fuck You, so I’m going to offer you a challenge, find someway to make your dick bigger then mine and I’ll be your sex **** but if you don’t win, I will fuck You in both of your holes till your raw, then I’ll fuck your girlfriend till she is just begging me to keep going!” she said seriously but knew that it was impossible, so she walked out of your room laughing then slammed the door.