Until recently the exact nature of Ji Cheong-sin's relationship with Bae Sang-pil, the man he called "father" was unclear. I laboured under the impression that Cheong-sin might have been some kind of illegitimate son that he kept hidden while schooling him in the art of getting his hands dirty so that nasty rich people don't have to. That seemed particularly heartless but knowing now that Bae Sang-pil had adopted him for the sole purpose of training him to be a hitman doesn't make me feel any better about Bae Sang-pil. There's something very wrong even about thinking "at least he didn't use his own flesh and blood to carry out his dirty deeds" in this context especially. Ji Cheong-sin was an orphan that was adopted not because someone wanted to help a child and give him a home but because he was a potentially useful pawn in other people's sinister machinations. (Except that it has all come back to bite every single one of them with some measure of poetic justice)
Of course Ji Cheong-sin is not the only orphan in the show. The increasingly uncanny and youngest Counter, So Mun was left orphaned in a staged vehicle accident all those years ago when his parents succumbed to their injuries. The line of fate linked these two orphans from that time and the irony is that Cheong-sin became the architect of his own downfall when he allowed Mun to live. Perhaps he was sympathetic to the boy's orphaned state or perhaps (a more likely scenario) he got a kick that he was instrumental in leaving another child orphaned in this world. As a result of all the terrible things people do in this show... we have two orphans that are contrasted consistently in the big story. One becomes a tortured villain and the other a superhero in the making.
Being an orphan isn't the worst thing to happen to anyone (as it is presumed by many in the culture) but as the show rightly points out, it is how the orphans are raised that matters. Thus there's a nature vs nurture theme woven through the storyline. So what's the difference between Ji Cheong and Mun? It's the kind of family they get adopted into that matters. It is natural for human beings to gravitate towards the idea of family whatever their background. Dysfunctional or supportive, family matters in how a child becomes an adult. Every time the two clash, the show reminds us that orphans can turn out very differently depending on how the nurturing that brings them to the position that they come to be at.
When Ji Cheong-sin returns to the orphanage, he declares that he has two surrogate fathers -- Bae Sang-pil who used his loner tendencies and turned him into a criminal as well as Lee Jung-yeong who exploited his currency as a prized commodity. Ji Cheong-sin knows what the children could become if they continue at the home so the part of him that's retained some degree of humanity wants to save them from a bleak future. Long before the demon possessed him, young Cheong-sin was already on the path to destruction because of the evil intent of humans. In better hands, it is suggested here, he might have turned out differently.
As I've said previously here and elsewhere, long before Mun became a Counter he was already a hero because even with his physical disability, he stood up to bullies and cared for his ageing grandparents good naturedly. His trajectory is deliberately antithetical to Cheong-sin's. The equally heroic Ha-na too was left orphaned after the death of her entire family although we aren't privy yet to the all the circumstances leading up to the family tragedy.
Orphans rate special mention all over the Bible in relation to their status (or non-status) as members of the vulnerable in society. They are to be protected and cared for rather than exploited because they have no one. It is just in the biblical worldview for the stronger to take care of the weak.
The orphan motif is also to my mind a metaphor for isolation and loneliness. The children at the orphanage are out in a remote area away from public scrutiny so they are especially vulnerable. It is a convenient location for all kinds of skullduggery to take place. Even when adopted Ji Cheong-sin was never part of Bae Sang-pil's family. He slept at the wrecking yard in a makeshift room although he craved a real father-son relationship with Bae Sang-pil. Since coming into the spotlight, his fugitive status has seen him living an increasingly transient existence hopping from one place to the next to evade capture. He has no home so even when he goes back to the orphanage, it cannot be home for him. He has become a danger to the children and himself. The demon which might have offered some measure of companionship has made him completely alone. Moreover Baek Hyang-hee is not much of a companion -- as there's really no honour among thieves.
While they are a family, the Counters are forced to be isolated for the rest of society and not get involved in human affairs. Which is impossible. Their secret necessarily means that they cannot tell people the most important feature about themselves because they have a higher "calling" that they are compelled to keep mum about.
Detective Kim Jeong-yeong was isolated in her workplace because of her integrity. The corruption at the very top meant that she would be considered a pariah by her colleagues for clinging on to her ideals regarding the job. Before the rookie, Kang Han-ul joined her one-woman team, she was working alone and hampered at every side. She was "orphaned" ie. ostracized from her context. On top of that, Mo-tak had no memory of their relationship and so she really had no one for a really long time in the force.
In an unfortunate case of good-intentions gone awry, one of the orphans stops Mun from summoning the demon from Cheong-sin. This gives Cheong-sin an opportunity to take his own life to disrupt things for Mun. It's not certain if that's the evil spirit or the man at work. They could be acting in concert. What's clear though is that there is no second chance for Ji Cheong-sin. Evil has so gripped him that he's reached a place of no return. He is sacrificed for the demon's longer term survival.