Ryll said Ririka was a former captain, but none of the characters have ever really hinted as such. The only back-up is that she wore the hat in one of the pictures Marika found on the internet, and that she's well known around the place (everyone knows a famous pirate ship's captain.. but rarely does the name Misa or Kane get spread around).
The mask means mystery man. I can only think of one mystery man.
I would have thought of scars too, indicating that he survived whatever horrific injury the crew thought he fell fatal to. Now that I remember.. they said he actually died of food poisoning...
(/me expecting some gag about him experimenting on a recipe with new native ingredients on an exotic planet and fell into a near-death state)