(warning: it may not be 100% faithful because I haven't finished reading the manga, plus I made some adaptations to make it better)

summary: you are a guard in a city, one day you met Ramia, a hot, muscular and short woman, some things happened between you two, but nothing serious, to summarize, Ramia after a while solved a case and saved several women who were being kept as slaves by monsters, one of these women was your sister Clea, and you were very happy to see your sister again, and to summarize (again) now Ramia will train you and your sister