Mia

 Mia is a catgirl that can be found outside of Mill Village.  If you talk to her, she will join your team.

 She is your "express pet". You can use her to deliver items to other players if you are over level 10. You cannot express items if Mia is in battle mode, manufacturing or riding mode.

She is an Animal Type character. Her "Light Wall" skill protects the target from both physical and magical attacks. It breaks if one turn is up, if the target has been attacked three times or if "Wall Break" has been cast of the target.