Mukuware Nakatta Murabito A, Kizoku ni Hirowarete Dekiaisareru Ue ni, Jitsu wa Motteita Densetsu-kyuu no Kami Skill mo Kakusei shita

Everything we do unconsciously changes the world!! Mateo is reincarnated and picked up by a nobleman, who dotes on him and allows his abilities to blossom. He can hatch a dragon egg in an instant and use ancient magic. Hearing rumors of his great magical powers, the emperor comes to investigate, but it turns out that the emperor is actually a girl disguised as a man...!?