Just keep doing quests. They will lead you to more quests/missions. When done with those, you will be out of the island. FYI if you do all the quests, you will usually wind up leaving the island around level 17
You need to do Zen Daijun Mission. Upon completion you will go back to the Seitung Harbor where you will book passage to the mainland.
At lvl 9 not sure your close to that mission yet. You get it by following the storyline, you need road less traveled to take you to the harbor then from there you need to do the "looking for trouble" quest that will eventually end you at Zen Daijun mission area