Generally, I think the Kdrama version works fine with or without a sequel. Cos (ahem) after skimming through the plot of the original on Wikipedia, the Kdrama version, imo, is less complicated. In the original, I suppose the ending where the protagonist commits suicide (and yes, the suicide is “verified” in the sequel) ends a little abruptly. Whereas in Life (K-remake), Tae-joo’s re-entry into the current timeline also borders on dreamlike.
So while the original CLEARLY isn’t a “time-travelling” narrative, Life (K) can be seen as one. The modern doctors (aka Dr An Min-seok) write off Tae-joo’s nagging worries over the hallucinations and his deep seated feeling that the 1988 past is “real”, as his subconscious playing tricks on his conscious mind, and LOGICALLY speaking, it is possible. Tae-joo had major brain damage — even though it is not irreparable, his long time coma could have muddled him up. And we do know that pre-accident, he had taken the case files to look through, which contained pictures and details of the 1988 Homicide Team and how they died.
However, it is not possible to re-enter the 1988 time frame without another major concussion — hence the flying leap (of faith) off the building. Which is ironic in many layers. The Tae-joo in the 1988 was SO eager to return, he was willing to jump off a building in order to “wake up”. The 2018 Tae-joo eventually chose to do the same thing, to go back. And I find it very, very eerie that his MUM actually encouraged him to commit the act (although unknowingly). All her “follow your heart” etc spiel…if she knew her son was going to jump off a building after hearing that, I think she’d die of heartbreak.
Eventually, Tae-joo’s return to 2018 helped to round off the current case which landed him in 1988 in the first place. Whether it is his subconscious piecing together those info he read off the files, or he really experienced them full hand in 1988 is a moot point. End of the day, I feel Live let Tae-joo return mainly to close off the loop. It is so obvious he lives a much fuller life in his dream/ not-dream state as a 2nd-in-command under Team Leader Kang. He loves his team mates, and the first thing he did when he returned is to go around expressing how much he missed them. Which, for Tae-joo, who is so used to being alone and a veritable hedgehog, is a big step towards humanity.
Like what everyone tells him — the place where you smiled the happiest, is the place where you should belong. Regardless whether it’s real or not.