You would never have gotten to where you are now (your mother's basement) if you didn't know how to seize an opportunity by the throat and run with it. You just so happen to be in the market for a female companion, and here is an attractive young woman professing her love for you. The only problem is that you don't have much experience in the whole 'human interaction' field. While a Casanova type might try to talk to her, ask her out to dinner or the like, you feel much more comfortable just skipping straight to sex. Does it really matter that she's your sister? No, no it does not. (Well, actually, it kinda does.) Shut up.
"I HAVE WET DREAMS OF YOU ALMOST EVERY NIGHT! Oh my God, please forget that you heard that!" She says.
You respond by tackling her and carefully removing her clothes, it would be a dick move to damage or rip them while you are rapeing your sister.
"OH MY GOD I NEED YOU INSIDE ME SO BAD! No, wait don't listen to me! Its the ray gun talking! PLEASE FUCK ME! Please don't! YES!" She says. There is a noticeable lack of struggling on her part.
You fumble with her bra hooks, you can put a hamster on the moon (You couldn't figure out how to get it back though) but you can't manage to think of an easy to remove bra design.
You say, "But I'm so confused, should I do it or shouldn't I?"
"Don't do it! DO IT! No, don't! YES, DO IT PLEASE!"
"I heard the magic word, I'm gonna do it." You remove her panties and pull your throbbing dick out of your pants.
"Wait," You say. "I need your consent before I rape you." (Why?)
"I REALLY WANT TO CONSENT TO HAVING SEX WITH YOU, BIG BROTHER!" Now it's consensual rape. (oxymoron.) "But I know I shouldn't, please stop!"
"Too late, you already said you want it!" You plunge your Johnson into your own sister's vagina, both of you simultaneously lose your virginity.