They say the present is where one learns the lesson from their past and applies it for a better and more secure future. But why does it feel like the present is in a loop and the mistakes of the past and present keep repeating themselves over and over again; it's heart-wrenching and exhausting at the same time.
It makes complete sense that Sigma is from the future. His (Kim Byung Chul) re-entry into the present was indeed a violent one. I get the sense he works as part of an influential organization and not as an individual, or maybe he is the head of the organization, but he was too prepared to be a one-person team. But if he's from the future, he knows there's no changing it, but do they keep coming because it's possible to change the present; it's the one thing that keeps bothering me about the smugglers, even Sigma. They know they cannot change it, yet they keep coming. But just because one can't change the future doesn't mean they can't keep trying -- hope is the last thing ever lost.
Everyone has their own agenda and motives for why they either want Han Tae Sul dead or alive, be it from the present or the future, including Seo Hae, even though I think her agenda is more Tae Sul than anyone else. Outside of Sigma, the Beauru under Hwang Hyun Seung is the most dangerous because despite knowing the smugglers risk their lives to come to a doomed present, he continues to track them; it almost feels like he's doing it for a personal vendetta, which makes him that much more dangerous. The fact that he seems to be after Seo Hae more than Tae Sul makes me believe she holds the key to unlocking the mystery that is Sisyphus.
Knowing the kind of person Han Tae Sul is, I doubted he would invent the machine that would ultimately destroy the world. At first, I thought he would've built it for his brother, but then I realized Tae Sul doesn't want his brother smuggling to the present. So, the only other scenario that makes sense is he built it for Seo Hae as a way for her to find her way to him in the present since they no longer exist in the future. The same reason why she risks her all to find him and a way to change the future and ultimately save him and the world from annihilation.
On a separate note, I love Seo Hae in the future; she is determined, decisive, fast, and courageous, unlike herself in the present. She always seems to be second-guessing herself and fearful, which makes sense since she's more in her element in the future. Watch Episode 8 here.