Biryuu Enshoutan is a Manga/Manhwa/Manhua in english language, Adult series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.nl fastest updating comic site. The Summary is

Iver is a dragon maou who stopped trying after historical heroes defeated her every time she resurrected. But the present day her, Mirio, who found the holy sword by pure chance falls in love with her. And thus forms the couple of the maou with no self-esteem and the dopey hero. This is a story of how they come to know each other, fight, and find happiness.