Sora, the mischievous gyaru little sister now a schoolgirl, grows increasingly curious about sex. To seduce her beloved older brother, she actively learns dirty talk and becomes more skilled at using seductive words every day. No matter where he is in the house, she approaches him with vulgar language. She bursts into the bathroom, sneaks into his bedroom, or invites him into her room, teasing him in provocative poses. Each time, she taunts him with gyaru slang like, "Onii-chan... wanting to creampie your little sister? You're seriously a pervert, huh ♪" The highlight is watching her get drunk on sex, using everything she's learned. The charm lies in her pure curiosity as a sister and her gradual transformation into a woman.