SNK is based on the book "The Eternal Champion", and the characters seem to have references to characters in the book in this way:
Erekose (Protagonist) = Eren (They both swore "kill them all", and they are gonna die soon for a curse, they want be normal guys)
Iolinda (Human princess) = Mikasa (They are both very jealous and both accuse the protagonist of sympathizing with the enemy, remember Annie)
Ermizhad (Eldren princess... yeah her race is called Eldren and The Eternal Lover) = Historia (They are both blondes and have blue eyes, both had a sibling who had the key to unlock the ancient power of the Eldren people, remember Frieda)https://en.wikipedia.org/wiki/Eternal_Champion
Erekose reincarnates to be the savior of mankind and has dreams in which he can see his past and future lives (as the user of the coordinate can see his previous and future users). In addition he is stuck in a battle between two sides, humanity and the Eldren.
The Eldren have an old power that almost destroyed the world and its ruler has decided not to use it even if that means the extinction of its species -the 145th king-
He is destined to commit genocide of some kind, and at some point says "I swear I would kill them all"
Erekose sounds like Eren
Erekose loves Ermizhad, an Eldren princess who is described as a blond woman with blue eyes.
John Daker/Erekose carries the burden of remembering every incarnation he has ever had/ the coordinate.
Prince Arjavh is a stand in for both the 145th king and Armin