I believe the main issue with how bad it was is the story telling. Everything is a sequence of a sequence and it's not a causality, you're only told the cause when you're no longer interested in knowing. The situations aren't revealed, they seem to be tailor made to fit a very explicit and simple narrative.

I was expecting it to be at least average but it wasn't. It's boring, long, without a purpose and, as the episodes amount, it becomes unbearable.

I don't know how to put this, but at some point it seemed like ¡ncest. The leads look very physically alike, they could be siblings in real life. To add to that, they build a very strong and long friendship relationship without any signs of romance. They were raised like siblings, treat each other like strangers and then go back to behaving like siblings. It's like things just happen without a rhyme or a reason. Then they show you the reason but it feels like something they made up to account for what happened. It doesn't feel true.

The acting was too plastic, fake even. Over exaggerated fights and screams, they looked theatrical instead of believable. You can't portray truth if it isn't mildly believable.
The paramedic could be young at heart and like and maybe believe in superheroes without acting childish or speaking in a childish manner.
I don't blame the actors for any of this, actors do what directors and writers assign them to do.

There were some interesting themes but they weren't properly developed and I find that sad and a waste.

Something that has been bothering me is how Korean dramas portray the ownership of a restaurant as something the owner does themselves and by themselves. You can't physically be the cook, the dish washer, the waitress, etc of a restaurant. Restaurants are businesses, they need profit. You can't have two tables and say it's a restaurant, it won't have enough turnover to even break even. You can't have the same person who's cooking tending to the tables. Has anyone in the kdrama world ever worked in a restaurant or been in a restaurant and looked around? This is not the first kdrama that portrays restaurants in this manner. If, indeed, Koreans have to do all those things by themselves, then I guess that's a part of why they have a mental health crisis, because it's physically and mentally impossible to run a restaurant or even a café without staff.
Yes, this seems a very petty thing to have an issue with, but the little things are what makes a story believable or not. If it really works like that in South Korea, storytellers should be criticising how that's not sustainable or ideal, because it's not.

I'm leaving this review here because this platform seems to have a problem with real opinions that don't put their favourite media on the same pedestal they do.
We can only build better media by being honest in our opinions.