Soul Cartel follows Si-hun Cha, a young Korean boy who is able to see the spirits of the dead. He is taken care of by his older sister, Su-In Cha, and comes from a family of powerful mediums and exorcists. Si-hun Cha himself is lacking in any spiritual abilities whatsoever aside from his ability to see spirits. Despite this, he tries to help his sister catch weaker wayward ghosts. When chasing after one of these ghosts, he runs into a very powerful demon. The demon claims to be the Mephistopheles, or shortly, Mephisto, who wants Si-hun Cha to teach him of the modern human world and bring him books about his exploits. He states that if Si-hun Cha tries to run away, he's done for. Si-hun Cha does have the common sense to consult his sister (without revealing that he's actually caught a powerful demon's attention), but he quickly learns that even his sister would be no match for Mephisto. After Mephisto finishes a copy of Faust he reveals that he came to earth because Faust has been reincarnated. Faust was a human who'd claimed that he would not be corrupted by Mephisto's temptations, so they'd entered a contractual wager, with God acting as the judge. However, according to Mephisto, God had unfairly intervened at the last moment and cost Mephisto his victory.