CINDERELLA BOY

Ranma is a poor private detective with a strong sense of justice. His partner, Rella, is a thrill-seeking rich girl. They make for an odd couple on the dangerous streets of Kirin Town, until a run-in with a mafia boss ends up in a near-fatal car accident. Ranma wakes up at the scene, but it is days later and Rella is nowhere in sight. He gets back on the case to find out what happened to his partner, but at the stroke of midnight, a metamorphosis occurs, as Ranma is replaced by Rella. Now every day is a race against time as the two detectives, somehow working together though always apart, try to get their normal bodies back while taking on cases and struggling to survive against the city’s vilest villains. — Description from AniList community (anilist.co).