Onion Swordsman job - Register someone multiple communication IDs on Mog Net. Send seven messages to another player. Send and receive four messages from Topapa. After reading the fourth one, you will get a message giving you a mini-quest. Go to Uoul and talk to Topapa. Go to the cave that is to the north of the other cave. Enter, then defeat the three Bombs to get a piece of crystal. This will unlock the Onion Swordsman as a job.
Secret dungeon - Send seven mails to another player using Mog Net. Send four mails through Mog Net to the NPC "The 4 Elderly". Send four mails to "King Arusu". After reading the fourth one, you will unlock a new quest. Ride on the airship that can travel underwater and go to the floating island. Once there, go directly south until you see a shadow in the water. Go underwater at that point to enter a cave with a secret dungeon and Boss.