Perhaps I am in the wrong age/ mental group. I found this stuff messy and meaningless, more or less centered (since it's neither) about who deserves to be killed (based on what?).
The series jumps from one killing attempt to the next, akin to what happens in many videogames, a point of which people are reminded in the end when the screen goes "thanks for playing". As such it shares much with "Squid game", which I found to be trash.
I expected more from Lee Young-Ae, here juggling videogames, booze, junk food, and occasional work.
Some acting was OK. The best element of the series is the music; some cartoons on which the series is based, are also OK.
I am afraid that tossing the serial killer in jail (could have shown the trial!), who hears a jail mate screaming that some guy deserves to die (as if she needs that to lust after killing!), is a preamble for a second series whereby the nutcase escapes for a new killing spree. May God have mercy on us, and block "Inspector Koo 2".