Final Fantasy: Lost Stranger

Square Enix employee Shogo Sasaki has a big dream-to produce his very own Final Fantasy game with his sister, Yuko. But after the siblings are involved in a truck accident, they awaken to realize they've left their world behind...and fallen into the world of Final Fantasy! After coming to grips with the situation, they meet some new friends, join a party, and accept their fate as adventurers. But when danger approaches, Shogo will discover that his encyclopedic knowledge of the games can only take him so far...

(Source: MANGA UP!)