The authors developed a folktale generator system (FGS) based on the narrative function theory of Vladimir Propp which is used as the story grammar. FGS allows users to generate diverse story plots by drawing curves, intuitively. Each functional segment of Propp's theory in a story is modified into ten variations (including the original one), given a score attribute from one to ten, and then stored in a database as text scripts. Hence, by intuitively drawing a curve, variations can be selected from the database and connected together based on their scores to construct a new story. Thanks to the multitudinous possibilities of stories that it offers, FGS can bring a new breath to traditional folktales and enhance conserving its cultural values. It will also help directors and game designers in the fields of narrative and story design.