TL;DR - Worth a watch, but don't get overly invested.

If there is one way to sum up My Demon, it would be "wasted potential". It had a phenomenal cast, a plot that initially seems gripping, and a promising OST. But it then proceeds to spend 16 episodes doing nothing with each of those elements.

Starting with the OST, it immediately grips you episode one with TRUE - YOARI. But aside from True and Whenever Wherever, many of the songs quickly wear out their welcome due to repetition. It feels like the producers found a song for each emotion they wanted to evoke, and then just played that song to invoke a feeling, with no real diversity or writing to back it up. Perfect example - using the main song TRUE when Jung Gu Won returns to save Do Do Hee. Theoretically, a great scene, if we hadn't heard the song over and over, in addition to the scene just not really landing right due to improper build up.

Which brings us to the next issue - the writing team squandered a phenomenal hook with the plot by trying to shoehorn in every single kdrama trope you can imagine. Secret God hiding behind the scenes as a beggar? Check. Protagonist losing their OP powers to force tension? Check. Extremely forced break-up in the final act? Check. Weird trauma connecting the ML to FL to force said break up, without any proper explanation or payoff? Check. If they had just kept the plot focused on the murder of Chairwoman Joo and properly hidden the true killer better, it would have been a vastly more interesting show. Unfortunately, it quickly becomes apparent that Jung Gu Won will simply snap his fingers to get Do Do Hee out of any situation, but then oddly not actually see it through immediately, because then we'd have no show. This becomes increasingly apparent when they keep randomly mentioning Jung Gu Won's need to fill contracts as a demon, but only when they need to manufacture a time crunch to remind the audience they should actually be caring about the demon vs god plotline instead of the murder mystery part.

The only thing that saves the show from being totally bland and average is the chemistry between the cast. Both the ML/FL and the SML/SFL make adorable couples with tons of great moments. it feels like they were written by an entire separate team of writers compared to the rest of the plot. Watching Jung Gu Won awkwardly try to play homemaker with Do Do Hee was some of the best moments of the show. It's just a shame that it comes grinding to a halt when they decide to shoehorn in the weird connection of Jung Gu Won actually having signed a deal with Do Do Hee's father and being there on the day of his death. It's clear they were trying to force a confrontation by trying to make Jung Gu Won responsible for Do Do Hee's parents' death, but it isn't written well enough to make sense. He never actually does anything to her parents, but then basically dumps her and runs away out of shame, only to come back and then they never really address it as a couple? It is entirely overshadowed by the fact that she dies to save him, and then he resurrects her and dies himself for breaking one of God's rules. It felt incredibly hamfisted, like the writing team needed to hit a set number of cliches per episode so they forced it in there to be more like Goblin King or Tale of the Nine Tailed. After all, what good is a fantasy kdrama without the MC "dying" in the penultimate episode?

So overall, it is a perfectly serviceable show, just not very unique. Each thing it does is simply done better, in another show. Want ill-fated romance and tragedy? Goblin King. MC with cool superpowers that chooses to give it up to be with FL? Tale of the Nine-Tailed. Tragic past-lives connection? Destined with You. Burning chemistry between the leads with a romance that will both make you laugh and sob at the same time? Crash Landing on You. My Demon is basically an amalgamation of a bunch of different shows, and it does each thing just slightly worse than the show it's copying.