I dropped it in the fifth episode but I skipped forward to see what happens in the next episodes and... I guess it's okay if you have nothing better to watch or it is one of your first kdramas ever, but for someone who's seen dozens of them the execution of the story is not interesting enough to keep you hooked.
From the start there are quite a few unanswered questions, and I dont mean the main intrigue here ... I haven't read the webtoon but in the drama you can immediately tell that we are talking AI here and not some man's soul trapped in a smartphone [since the kdrama's universe does not have any magical elements]. The relationship between Park Inseong and the CEO is cute at times but you just can't help thinking that this man's body is lying somewhere/he might be already dead and here we got two grown-ass people who somehow believe that someone's soul could be trapped in a smartphone.
We also don't know how, if its just an AI, CEO's smartphone ended up sending calls for help? Was it just because he witnessed the whole situation? It's unclear.
I think it would've been better if they had figured out very fast that the smartphone CEO is just an AI and tried to solve the mystery starting from there... maybe that would make it an 8-episode series and I wouldn't complain.
I do admit it was kind of funny though seeing obvious "Parasite" references in the earlier episodes.