Kelvin

Kelvin beat Sylvia in a fight and is now an S-Rank adventurer. His job is "Green Priest" on his Adventurer's card. He is referred to as the Black Summoner by Tristan Faze, the General of the Monster Army from Trisen Empire. He is also known as the Shinigami because he uses a scythe as a weapon.

(Source: Kuro no Shoukanshi Wiki)