Unmei no Tsugai ga Omae da Nante

As an omega, a type of secondary sex that allows an individual to give birth regardless of their primary sex, Yuu Shishikura has always dreamed of starting a family. However, he sadly remains the last of his friends to find a spouse. As he fruitlessly attends mixers and solicits matchmakers, Shishikura's peaceful professional life is invaded by a new coworker, Haruto Kotani, who still resents him from their time together in middle school. When fate leads the two to meet in a love hotel during Shishikura's heat, the ensuing night of passion changes their relationship in ways that neither of them ever expected.