This is a story about an ignorant younger sister with a developed body who receives incorrect sex education and becomes curious. She starts touching her brother's penis, asking "Can I insert it?" Due to a lack of knowledge about incest, she doesn't realize when he ejaculates inside her during intercourse. She performs vigorous thrusts and cowgirl position, experiencing multiple orgasms. The brother tells her that rubbing sperm on her skin will make her beautiful, so she decides to try it. Eager to grow up quickly, the sister is interested in beauty and exposes her breasts to support her brother's masturbation. She splashes semen on her thick thighs and performs handjobs and blowjobs, even licking his testicles. The sister asks, "Can I insert this (penis)?" As her brother licks her nipples and removes her panties, he reveals her developed pubic hair and vagina. Embarrassed, she asks, "Why is it open?... No! It's embarrassing." When her brother plays with her vagina, she can't help but moan in pleasure. Manual stimulation brings her to orgasm, "I haven't come yet! Where are you licking?" As he performs cunnilingus, she moans uncontrollably. When he presents his erect penis, she innocently focuses on licking their genitals together. The sister says, "Ah... uhh! Brother! That's not allowed! No!" Finally, in a non-stop cowgirl position, semen overflows from their joined parts, and she exclaims, "Ah... it's warm... so much came out."
