Aeirik Ryu Han-Bin

Eric (or Aeric) is the main protagonist of the story. His real name is Ryu Han-Bin, which he had changed to Eric to conceal his identity as an Otherworlder (humans that originate from Earth.) Later, under his disguise as a Valterian Warrior, he calls himself Feladd Bin.

(Source: Survival Story of a Sword King in a Fantasy World Wiki)