A Ferocious Beast in Another World

A textbook straight guy wakes up on a planet of beastmen, a place he'd only ever read about in novels and never seen with his own eyes. The problem is, this beastman world seems to have a rather strange set of rules... Other humans who arrive in the beastman world become females, the submissive partners, protected, cherished, and lovingly cared for. So why did he become a female too, but one who's the dominant partner?! Wait, why do these ferocious-looking beasts act like tough men breaking horses by day, then shed their human skins at night and turn into huge beastmen waiting to be "fed"?! Sure, he's straight, but with beastmen on the prowl, what is a poor human supposed to do after getting caught by a domineering, gentle, and damn strong beast... And then, oops, he hears that the beast is pregnant? Theme: