Akogare no Onee-chan wa Choukyou Shigansha?!

Since our childhood she was in my thoughts. I yearned for her.
Then she spoke the words that changed both our worlds:
"I want you... to debase me... like this."
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Imagine if the girl next door had a humiliation/submission fetish!! There's no turning down "tie me up"... she wants to be helpless in your command. As your sex trainee, show her how to fulfill your darkest fantasies, and rendered prostrate, her eyes soft, her breasts bare, unleash all erotic inhibitions.
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Bondage hentai. Break her soul and she's yours forever. Explore the darkness.
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"I'm a delicate flower."
Those were more the words that suited this demure and beautiful onee-san.
We'd studied together, even in my own bedroom, but had she ever seen me as a man? I didn't know. I simply drank in her presence. As the tension mounted one day I had to buy a dirty magazine and relieve myself. It was a shocking BDSM magazine, full of girls in ropes with legs split over torture wedges...
I'd opened a door to a world... that neither of us knew...
And she saw the magazine, and we entered that world together...
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"Will you do this to me? Please?"
The words were timid yet searingly intense, and my blood rushed hot.
I pushed her to her knees and twisted her arm. She was scared yet excited.
The process had begun.

[from DLsite English]