She wanted to, probablyWhat's the purpose of his sister watching all that shit ? To Provide first aid ?
She offered herself and had sex with her (not blood related) brother. She's there because she's horny.What's the purpose of his sister watching all that shit ? To Provide first aid ?
To get enough of the heroic sex madness pumped out of her brother so she could have "normal" sex with him (implication of last 3 panels on page 21)What's the purpose of his sister watching all that shit ? To Provide first aid ?
To heal the female participants so they can continue and not die physically, or to stop him if it looks like they're about to break mentally.What's the purpose of his sister watching all that shit ? To Provide first aid ?