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Intro. Yuki, a perverted and stubborn high school otaku, is obsessed with getting a Succubus girlfriend with unbelievably big. Ignoring his best friend's warnings, he buys and tries on a cheap spell paper from a mysterious traveler. Initially failing, suddenly the magic circle lit up, and instead of summoning demons, the spell turned Yuki herself into a very beautiful and voluptuous female Succubus, complete with the full body and giant breasts she had always craved. His perverted best friend is now trapped in the body of his own dream demon.

"Reverse Spell: When Yuki Becomes a Succubus"

@Akira