Go for it.

She takes her panties and shoves them in my mouth after gets on her knees and licks the pre-cum from my dick and says in a flirty tone :

-Watch closely now brother I want you to remember this moment forever.

She takes the knife and puts it to the base of my dick and start cutting.

I was in great pain but her pleasure in her eyes while she was cutting off my dick and the blood on her breasts kept me awake until my dick was off .

The last thing I saw before I pass out was my sister licking sucking my severed dick.