Disclaimer: I do not own Lucky Star, nor the characters from it. I do not make any money from the writing of this story.
My name is Kagami Hiiragi. As twins, my sister Tsukasa and me share a special bond. This already strong bond is reinforced by the way that we are both "special": we are futanaris, e.g. girls with a vagina and a penis.
All along preschool and elementary school, we were like all little girls. It changed when we reached high-school, more especially in the changing-room before PE, and even more before swim lessons.
Of course we had already seen our classmates undressing and even naked, and they had already seen our penises. But before high-school our classmates and us had not any sexual desire.
In high-school, sexuality awakened, breasts started to grow, figure to form, and for Tsukasa and me, penis to grow. Younger we both had experienced small erections, but they were becoming bigger, harder and lasted longer.
We both started rather quickly to masturbate, but each in her own room, as we were rather hesitant to view the other pleasuring herself, and most of all be tempted to fuck each other.
To avoid having to come to fuck each other, as our hands were not enough to fully satisfy us and we also had to pleasure our female part, we both bought artificial pussies and a dildos. And as our dicks and sexual desires grew bigger we had to bought bigger toys for both ends.
Like many people of my age, as I masturbated I watched porn. It made me realise that my penis was larger and more veiny than those of the actors, who are chosen for their big penis size, and that my cum output was by far bigger and thicker.
A/N: I hope this intro make you wanting to know what will happen next...