Remnant: Juujin Omegaverse

Daato and his younger sister Bella are two orphaned omegas living in an orphanage. Because they're omegas, the two are destined to be married off once their first heat comes around, but Daato can't stand the thought of losing his only family. And when Bella suddenly goes into heat, Daato learns that the priest hasn't been marrying off omegas but selling them off instead! Determined to keep his sister safe, Daato's only hope is to seek help from the mysterious alpha beastman named Juda. With everything on the line, is Daato making the right decision, or will the siblings find themselves in even more dire straits?

(Source: Seven Seas Entertainment)