In the Mayonaka no Hero series:

V.1 - Night Shade
Colt Nightshade: Professional troubleshooter. A damn good man to know--if he's on your side...

Althea Grayson: That's Lieutenant Althea Grayson--a hell of a cop, and heaven in his arms.

Colt Nightshade made his living facing danger--alone. But his search for a runaway girl through the steamy side of the city was one time he had to have help--whether he liked it or not. And if a man had to have a partner, he could do a whole lot worse than Althea Grayson. She was all business...and embodied his every pleasure. Soon, trouble became a four-letter word called love!

V.2 - Night Smoke
Ryan Piasecki: A man's man. A woman's fantasy. The kind of guy who got the job done, no matter what the obstacles...or how beautiful they were.

Natalie Fletcher: Cool, calm, collected. Until someone started making trouble for her business...and he showed up.

Arson investigator Ryan Piasecki came from the street, and he wasn't exactly the type to make nice with an upper-crust business executive like Natalie Fletcher. His business was fires - and his instincts told him the one at Fletcher Industries was no accident. They told him something else, too - that the sparks flying between him and this very classy lady had all the makings of a five-alarm blaze..

Descriptions taken from fictiondb.