Esther has a very symbolic role in the Scarf Heroes lore. He is the first to establish a theory in regards to the sanity levels of the population in the Old World. This theory involves every human having a soul, which is slowly fading away depending on determination and passion. Other factors are included to this such as life events and trauma, and overall support from friends and family.
The reason he has a fairly healthy soul is because albeit he does not enjoy living, he does find solace in hunting "demons" that absorb the souls of others. He labels them however he chooses, mainly when he has a funny feeling about how they act or the characteristic of their abilities.
He is the guardian angel representation of all characters, an individual that silently defends others without their knowledge of him even being there.