First mention on Day 148.
Otherworlders are refer to those, just like Rou, who came from a different world. These individuals carry the tittle [He/She from an Unknown Land] and possess strength that even matches Boss level monsters.
The 【Great God】 that controls ≪Space-time and the Star Ocean≫ is the one responsible for such things. When someone is invited here, the main body’s soul is copied from the other world and reproduced in this world as a new existence. Their new body which the 【Great God】 had prepared, becomes the real thing. Therefore, even people who had no capability to fight would, as a result, be able to do so.
They can percieve each other.