Onii-chan Nechatta?

Cute little sister spends all day every day with the brother she adores. They play games, they take baths, at bedtime she cradles his head in her lap. "Oniichan...... You're asleep, right? Definitely not awake......" Late at night, she gives him secret kisses and things. But the things have grown more daring... and now little sister has crossed a line. "I want oniichan's penis inside me..."