The main theme of this episode is separation and harsh reality intervening and crashing down on Mu Deok and Wook’s relationship just when they’ve realised they care for each other. Until now, they lived in their own little bubble - two outcasts and underdogs no one gave a damn about, but now Wook has become the hot commodity and bright star everyone wants a piece of and to bask in his light.
He has always been rich, handsome and noble, but now he is even powerful and power attracts. He stops being a pariah, yet she stays being Mu Deok - the lowborn personal servant he bought himself from a brothel. The realisation first hits Mu Deok after their sweet embrace especially hard because Wook always treats her as his equal, sometimes even with a hint of reverence as his master, not once has he made her aware she might be someone lesser. She has grown used to his gentle smiles and tender touches, grown accustomed to his sweet embraces. As a result, whenever they are alone she leaves out the honorifics, speaks to him intimately and calls him by his name, just like when she wants to give him the raisin tree pill, but she abruptly stops herself because Maidservant Kim is there, calling him by his title, and there is something tragic in the way Mu Deok corrects herself and a hint of sadness in her eyes as her smile disappears as she begins to comprehend the divide between her and Wook even before the walls of Songrim separate him from her.
And then, when she begins to doubt herself and their relationship, Wook, in his typical fashion, throws away all the expectation society has of him and immediately shares that precious pill with his Mu Deok. He is so incredible soft with her, taking care of her in all these different ways, and no one has ever been soft with her since her family died, except for Yul but that was such a brief time in her childhood while now, she is an adult woman.
That said, Daeho is not some modern haven of equality, it may be magical but the caste system still rules the society - a society where five powerful mage families rules and consolidate their power through constant intermarriages, just like any real world royalty or nobility, a society where a nobleman doesn’t normally marry his lowborn maid.
The literal wall that separates them only serves as a symbol for all the figurative obstacles keeping them apart. Now, Yun Ok appears - the perfect bride material from the perfect family, with perfect pedigree and physically resembling his dead mother - she is yet another remainder of the divide between Wook and Mu Deok, of what Wook life would have looked like if his father didn’t cut off his energy. The moment he escapes one marriage of convenience, Heo Yeom tries to force him into another, regardless of his feelings on the matter.
Wook and Mu Deok embody the ultimate star-crossed lovers: a man of noble birth who falls in love not merely with his lowborn servant, but with a murderous soul-shifting assassin who happens to be the biggest enemy of the kingdom and whose mere existence is considered a sin against nature, ergo their love is a sin. Moreover, she is older than him, is his teacher and he is her master who bought her; and if that all weren’t enought she is on borrowed time and can die on him any moment.
In the end, it’s them against the whole world, and Wook’s heated conversation with Park Jin and his defiance reveal to what lengths he is willing to go to protect Mu Deok and be with her. If he ends up being a pariah again and a sinner in the process, so be it, he can live with it, as long as he can spend that life with her.
