This is a weird male reader combination but, hope yall like it.
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You are a Yakuza from a small Family named Kurohyou-Gumi. Your boss, Masao. Is an avid fan of Horse-Girls including their Races and Idol concerts. He had a brilliant idea that he would get a horse-girl, and he did. For what? Money. Since your family are still new, they needed the funds to be big, you obliged and went to get the Horse-Girl. And here on out, your story as a Horse-Girl trainer starts here.