Naomi began to grow younger by the second. By the time Yukiko realized this and withdrew her nipple from the human's mouth, it was too late. The enchantment had taken hold.
Naomi's body began shrinking as it de-aged, vanishing when it became no bigger than a human toe. When Yukiko's belly expanded even more, she realized she had impregnated herself with Naomi as well.
"I didn't expect this." Yukiko said to herself. "Now I'll have TWO beautiful fairies to raise as my own!"