My girlfriend is Evil Dragon is a Manga/Manhwa/Manhua in english language, Ecchi 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

原本要救的公主竟然是恶龙，方士同学招架的住吗？恶龙小公主、女扮男装的长腿美女、合法萝莉师姐、随身携带“凶器”的师妹……来自东大陆的方士拾夜在西方大陆扮猪吃老虎的福利之旅，由此展开！ This adventure started with a young alchemist, who tried to rescue a princess, but this princess turned out to be a dragon. What will result in this strange, but funny meeting?