@AbyssalMonkey That's certainly a possibility, though his corpse disappearing and reappearing alive somewhere looks more supernatural than sci-fi, if you want my opinion.
And it's both a marketing ploy and a real conducing thread connecting the series. If you look around in Google, there's a timeline showing where every series is.
Most of the series only supply characters for cameos in others, but it seems RM and TM, as well as Neolith Girl, are at the real core of the universe and have plots that somehow contribute to each other. That's why Jung Woo's childhood friend is the main villain in RM.
I hear that now seasons 2 of both RM and TM are ending in Korea, there's a bunch of speculation that the two series will cross over in their next installment.
Still, this is much more well-done than DC and Marvel in the West, which I can't stand. You can perfectly enjoy TM and RM as standalone series. I for one only read RM, my familiarity with TM comes from working on the recent chapters, but I haven't read it from chapter 1.