Pretty Policeman by Fifer Rose

Detective Micah Hart wasn’t sure when his fairly safe, predictable life became something more closely resembling a dumpster fire.

But if he had to pinpoint an exact moment, he would say it was the first time he went undercover as a prostitute in an attempt to bait the notorious serial killer who was stalking New York City’s streets – the media-dubbed Hooker Hunter.
It’s when Damon Romano plows into his life, with his fierce protective energy, and those thick thighs, and the bluest pair of eyes Micah has ever seen.
If only he wasn’t also a temperamental mafioso in charge of running one of the city’s largest criminal empires.
Damon fixates on Micah, obsessing over feeding him and making sure he always has a coat. He spoils him rotten with gifts and insists on taking Micah on as his personal escort – a “boyfriend” to get his nagging sisters off his back.
It’s weirdly sweet, and Micah doesn’t know how he’s become a soft spot in the ruthless man’s otherwise hardened exterior, but it would be a lie to say he didn’t want even more: a real relationship with Damon.
There was just one teensy, tiny problem with that.
Despite what Damon thinks, Micah isn’t actually a prostitute. He’s a cop for the NYPD.

Pretty Policeman is an MM billionaire/mafia romance, sprinkled liberally with rom-com elements, served with a side helping of sugar daddy kink and mistaken identity trope.