MC and other players doesn't know, but Mikami will refer to Souta as a deity.
Turns out that there were other players that came before them, all their current dungeon knowledge is thanks to them in the beginning it was only four, Aurora one of them went to Europe and founded her country The Holy Empire, another went to Brazil literally, one is in the Middle East and the last one is in Japan currently she's Sera's Great Grandmother (She still looks like an 18-year-old girl) and the one behind the Saint Agency.
Basically, they have great influence on the countries they reside, even Mikami is reluctant to mess up with the Saint Agency.
After the fight with Tsukishima, Mikami starts to believe that Souta might be a deity like them and wants to bring him under her wing.
Kuga refers to Souta as aurora's apostle becuase he used a skill that belongs to the knight job and to become a knight one has to be acknowledged by Aurora herself (One of the first players) and become her vassal.