Dobin our MC gets charged with murder despite shooting a murder suspect (the Mixer/Propeller dude) who was holding Hamju (the Locker) hostage while the dam was about to break and kill them both. Like who charges a cop for saving the hostage in such a life-threatening situation?? Is Korean law really like that?
And of course, since the Propeller dude used his ability to break the dam, the other police officers don't know he did this because they can't see the mixer devices; but they were attacked by the Propeller! so the Propeller getting shot by Dobin (a police officer) shouldn't be that surprising! It's crazy that the they all label it as a cop killing an innocent suspect in cold blood. The storytelling takes a nosedive, really. And Jisu the stats girl was rarely given screen time throughout this long arc of 30 episodes.
The contradiction: episodes 88-89 show the cops with a SWAT team shoot Dobin on sight several times. Even though he was unarmed. Because they are starting to believe the theory that he's an Opener so he's suspect. But they don't even have proof -_- so you can't argue that he's armed. Meanwhile, no SWAT team was used for Propeller, a murder suspect who stated out loud he wanted to kill people. 0_0
And in episode 89, it's supposed to be sad how the lovers can't be together (I still don't ship Hamju with Dobin even if the title is Locker & Opener since their relationship is too cliche/not entirely healthy, but they do look cute together).
So the situation is there's a nationwide manhunt in Korea for the Locker (Hamju) and so Dobin who is in jail of his own volition decides to save her by escaping (since he's the Opener and also got a power up from the Knitter hands thing to open remotely). It's supposed to be a tragedy because Dobin doesn't plan on leaving the country since he helped a lot of people by opening stuff (eg: hearts) so if he leaves the 500km radius, lots of people will die or be affected. So he wants Hamju to leave and she doens't want to leave without him (flying to Greece to escape). So how is she convinced to leave: Hamju locks Dobin from her mind to make sure she won't miss him to "convince him to survive and unlock her memory of him", and also insisting Dobin obsess over her by getting him to open his own heart and insert a picture of her so he will always look for her as long as he's alive. It's supposed to be tragic but honestly it seems like Hamju has it pretty good if she does that so it's not that tragic for her (thus tragedy is unconvincing at least for her).
It seems like everything will end tragically but it's a happy ending. Hamju only does jobs that are meaningful and help people instead of for money. Dobin gets released after 8 years of prison. He finds Hamju, unlocks her lock and she remembers him, the end. One thing that didn't make sense was that now Dobin travels around the world with Hamju to do good deeds, but wasn't there a range limitation for their devices or did the author forget that Dobin didn't want to leave the country a few episodes ago for this main reason? Maybe they got an upgrade that wasn't told to the readers lol.

there were some plot holes but the story overall was still very enjoyable before the Propeller arc:
- in the first 15 episodes, MC (the opener, a cop) gets the locker (female, antagonist) kicked off a tall crane and so paramedics send her to the ER. he doesn't know which hospital but instead of checking nearby hospitals (what better time to find her while she's getting treatment right?), he has to track her down all over again. that's just dumb. the funny thing was he looked for stab victims using this method before (searching nearby hospitals) so it's mainly the author's fault here. author likely just forgot this method of looking for a suspect.

- Miss Locker gets open heart surgery after MC tries killing her by opening her heart valves with his power but she's up and walking after 5 days. sure, let's say the doctor discharging her after 5 days from surgery was plausible. but she's not going to be putting on clothes like there's no wound on her chest that's even painted red by the author as if it's still leaking blood -_- her ribs were opened! make it make sense. she even runs about and lies on her stomach and chest after getting discharged. it's a glaring plot hole when the author took the time to describe in DETAIL the medical terms of her heart surgery like mitral valve replacement being one of the simpler terms they explained. 0_0
(edit: later on, it's mentioned that they are given quicker healing as part of an upgrade to their abilities by 'the maker/knitter hands' that gifted them the abilities from the cosmos...)

- when the mixer/propeller ability guy gets kicked through the window by our MC (ignoring the fact that korean windows shatter way too easily; in the first 15 episodes the villainous Ms. Locker also somehow did the same thing with our MC lol) the mixer dude falls all the way to ground floor. he somehow gets saved by landing on bushes. the ridiculous thing was that the police finds him and exclaim "look how twisted his neck is! he needs to see a doctor quick!" and then proceeds to piggy back him to the hospital 0_0
did those police officers not receive first aid training? is it not a thing in korea for first responders to know basic things like if someone's spinal cord is possibly affected, you DON'T move them??
if the author wasn't so big on medical stuff in this story like talking about anti-coagulants, this wouldn't have been so irritating to see. but honestly it was also kind of hilarious how they just carried off the dude in such a comedic fashion that maybe the author did it on purpose. who knows. But obviously, Mixer's weird angle neck was because of Hamju's lock which is invisible to non-ability users -_-