Evoland Legendary Edition

After the great disaster, travel to the cursed island (past). Talk to Robert the pirate captain and promise to help him. Travel to the docks of Genova and talk to the girl near the sea, travel back to Robert and he will hand you a pirate flag.
Travel to the volcano island in the present and fight your way through the island. After succesfully leaving the island by boat after defeating the boss, you will get the achievement.