Tom: Are you sure?

Sarah: Yes!

Tom took off his clothes. He was now naked and Sarah let the symbiote cover every part of her except head and neck. Tom then started fucking her. He held his hands on his sister's breasts and put his erect dick into his sister's symbiotic pussy. The symbiotic slime covered it as well. She started to orgasm.

Sarah: Ah! Yes! Fuck... Ah! I'm gonna cum!

She then blasted a load of green goo and Tom's dick swallowed all of it greedily. Sarah then put her clawed hands on Tom and force his mouth onto her lips.

Sarah: Tom, you will not survive this sex session. I will give you a symbiote for you to continue!

She then smashed her lips onto her brother's mouth and a large symbiotic tendril came out from her throat and entered Tom's body. It covered him whole and he became much more muscular.