Kuro Kawa to Akunin

Alphas of the upper class cannot mate with Omegas without the king's permission, and Omegas are under the control of the state... In this country, there is a high-class brothel called "The Academy" where one can secretly test compatibility with an Omega. At The Academy, handsome Omegas, all wearing collars around their necks to prevent complaints from customers, are gathered under the direction of the director, Knox. In a school where various stories unfold every night, a noble Omega whose mate has already been decided comes to visit on his own accord...!?