Gyeongseong Detective Agency is a Manga/Manhwa/Manhua in english language, Drama series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Gyeongseong, a city of dazzling night and splendid desire. The door of the Gyeongseong Detective Agency, located at 45 Iljeong-mok, Myeongchi-jeong, is open. An orphan with no one to rely on, Sohwa, a 16-year-old girl with nothing but courage, is caught in a secret trap. "No, I don't know anything, I swear!" Jung Haekyung, a young man who runs a detective agency by himself. A chance encounter with a girl triggers memories of a past he'd rather forget, and Haekyung sets out to save Sohwa, who has been falsely accused. "If I tell you my name, will you search all over Gyeongseong to find me?"