Nyotai-ka shita Boku wo Kishi-sama-tachi ga Nerattemasu: Otoko ni Modoru Tame ni wa Dakareru shika Arimasen!

Alto, a novice librarian, is cursed to turn into a woman at sundown. To turn back into a man, he has to sleep with other men! Alto confesses his problem to the handsome bad-boy knight Sir Lloyd, who's only too happy to help him out. Alto shouldn't be enjoying this, but why does it feel so good!? And then there's Sir Lune, the well-mannered knight-in-shining-armor Alto has always admired, who's worried about Alto, too... Enjoy this one-of-a-kind story!

(Source: Renta!)