Commenter John Payne from the Man vs Drama YouTube threads writes:
The chance encounter between Dong Hoon and Ji An to complete My Mister is magical, from the onset when Ji An hears the voice she had become so intimate with, to the camera as it follows her over the shoulder to reveal a reborn young woman, standing in the beautiful sunlight and finishing with a handshake that is anything but.
It’s wonderful that Ji An, the mentor, has seen her student Dong Hoon become so happy. BUT WAIT, you may be thinking, Dong Hoon is obviously the mentor here. Hear me out though as I make my case. I think the Writer, Park Hae Young is brilliantly flipping the obvious roles of mentor/mentee here in ways that on the surface appear one way but in actuality are reversed.
As souls go, Ji An has declared herself to be the elder by at least 30,000 years. She’s world weary and wise but has forgotten her humanity. She’s tasked with destroying an innocent, and Dong Hoon though older, is naively and idealistically hanging on to a job and marriage that he is cluless about.
Ji An at first seems to take delight in destroying his life, but the one ember of her humanity left, her grandmother, is blown back into life by Park Dong Hoon.
When she tells him about the phone booth, she’s making a conscious decision to reveal to him the truth about what’s happening in his life. She’s the master here, a manipulator who sees every angle and is in control. But, Dong Hoon’s goodness and spirit begin to remind her of what she has lost. She’s the prime force for change in Dong Hoon’s life for good or ill. Dong Hoon though moral is stuck, he’s unable to move and his structure is starting to crack. Ji An wakes Dong Hoon up and when he begins to run towards her finally starts to make a change in his life.
It is Ji An who has shown Dong Hoon the truth, initially she is the teacher. Dong Hoon acknowledges this to her when he says, “Thank you, I was on the verge of death but you saved me”. Is this something the mentor says to the student?
The title of the drama says it all: “My Mister” or in Korean “My Ajusshi”, it’s not “My Anjuin” (My Mistress). Yes, in this process the student teaches the teacher, and this is what happens to Ji An as she wakes up to her humanity. By making the decision to save Dong Hoon she saves herself — and he can finally ask her, “Have you found comfort?”