Katsubou Anima Gemella

Hijiri Kaisei, an alpha, has issues getting close to omegas because he feels guilty over a traumatic incident from his past. Then one day, his senpai tricked him into going to a male omega brothel. While there, he meets Ryuji, a bitchy-maso boy, who is surprisingly different from the other omegas Kaisei met in the past. Will this encounter throw Kaisei into an even darker abyss..?! "The animal's burning desire"(Source: Takeshobo, translated)