Onii-chan Denki Anma Shite…

Cute little sister has a massive squirting orgasm with a vibrator in front of her brother's eyes! She's innocent and obedient, and her brother teaches her all about sex, giving her creampies and making her cum over and over!
(Source: Coolmic)
Note: Released in 50 episodes in long-strip format, and subsequently sold as 25 chapters in traditional format.