Anyone - Designated Free Use - Casual

Anyone:
Man, woman, or any beyond the binary as long as they're of legal age.

Designated Free Use:
Once per day, our protagonist is able to choose a single person who will then become free to use for the next 24 hours. This ruling will allow ANYONE to use the designated person for that day, but the chosen target will only defer their schedule for the protagonist. (You can give orders like "sit on this park bench until five guys bang you," while others can't; "That was a lovely creampie, but I should really head to work now.")

How our protagonist designates a person is up to artistic license. It can be stated, and subsequently acknowledged by the chosen party, written down on a notepad, scheduled on a calendar, or simply willed through horny thoughts. Once the target's 'shift' starts, their free-use can no longer be rescinded until the allotted 24 hours are up; however, the protagonist IS allowed to choose successive candidates to avoid 'free-use down time', as well as change designated successive candidates before their shift starts. (I.E. clock strikes midnight, the next chosen person is fair game, while the previous one is released from their obligation.)

Casual:
As far as loudly proclaiming someone is free to use, people will readily accept that information (as long as it's true). The designated target will accept their assigned role without complaint, and anybody shaking in their confidence towards being designated will at the very least have muted trepidation.

The general public won't bat an eye. Spouses won't look at it as infidelity. Law enforcement won't look at it as a crime. People may talk about what is happening but beyond that the scene is as normal as a warm loaf of bread in a window. Upon exposure to the designated target people will ask themselves one question only: am I horny?