Oretachi Unmei Janainoni!

For 10 years, omega Tosaka Jutta has been kept in a dungeon at an idol agency without a chance to debut. Suddenly, he’s given the opportunity to become the industry's first "mate idol" to promote the promising new star alpha, Yuu Takami, after a scandal threatens his career. On the surface, they act as the perfect “mates,” but Yuu, with his striking looks and exceptional acting skills, remains distant and cold toward Jutta, barely engaging with him. As Jutta attempts to connect with Yuu, things take an unexpected turn when, during a heat, Yuu catches him unintentionally making a nest out of his clothes...

(Source: Kaiohsha, translated)

Note: Chapter count includes an extra.