The penis becomes extremely sensitive when fixed at a vertical angle... The warm stockings that were tightly pressed against my sister's ass and thighs are now firmly holding my penis. Without using hands to fix it in place, I'm getting a blowjob with her erotic mouth. Unlike being held tightly by hand, this allows me to directly experience the sensation of her oral mucosa (the softness of her lips, the warmth inside her cheeks, the slickness of her tongue, the movement of her saliva...)
