Like a Dragon Gaiden: The Man Who Erased His Name

First you need to complete all silver matches as denoted in the guide below.



Second you need to be gold rank to unlock the gold matches. Next you need to have completed the sponsored gold match from the film enthusiast in the pool area. You do need to leave the castle and read her email first them talk to her again for it to unlock. Once you do the sponsored match and her gambling match, the achievement will unlock.