*this article has been updated to add corrected timelines, which includes actual years, which weren’t mentioned before episode 9-10*
“Sisyphus: The Myth” starring Park Shin Hye (as Seo Hae) and Jo Seung Woo (as Han Tae Sul) features a complex timeline.
The drama is about a man named Han Tae Sul who invented a way to transport particles from one place to another (probably the start of time travel via transporting bodies from one time period to another), and Seo Hae who travelled back in time — leaving her war-like future. Things get complicated when Han Tae Sul saw a wedding photo of him with Seo Hae, but both parties don’t even personally know each other.
The series seem to feature three different timelines: Seo Hae and Han Tae Sul who got married (2020-2035), Seo Hae who experienced war (2035), and Han Tae Sul who doesn’t know anything about time travel (2020).
These timelines revolve around the theory that:
The Seo Hae from the war in 2035 is the 9-year-old Seo Hae in Han Tae Sul’s timeline in 2020 and is also the Seo Hae at the wedding, which could be between 2020 – 2035. One is the current Seo Hae’s past (the child), another is her future (the one who got married). Although the marriage probably happened before 2035, it still counts as Seo Hae’s future since she went back to the past to try and save the world. She met and supposedly married Han Tae Sul, but gets attacked in the process. Thus, triggering the future where the nuclear war happened again. This means that Seo Hae could just be repeating everything until she stops the war. Hence, the myth of Sisyphus which is about repetition.

𝐇𝐞𝐫𝐞’𝐬 𝐚𝐧 𝐞𝐱𝐩𝐥𝐚𝐧𝐚𝐭𝐢𝐨𝐧 𝐨𝐟 𝐭𝐡𝐞 𝐭𝐡𝐫𝐞𝐞 𝐭𝐢𝐦𝐞𝐥𝐢𝐧𝐞𝐬:
• TIMELINE #1: SEO HAE FROM 2035
This timeline probably wouldn’t have existed if time travelling wasn’t possible, if the cause of the nuclear war had something to do with the time travelers. This is also the timeline where the Seo Hae we all know is from.
Regarding the diary, time traveler Seo Hae from 2020 was able to warn her past self (in 2035) through a diary she left behind, which eventually made its way to Seo Hae in 2035. This urged her to save her supposed-to-be-groom, Han Tae Sul — though she also doesn’t know him personally at this point — and led to her decision to travel back to 2020.
• TIMELINE #2: HAN TAE SUL FROM THE CURRENT TIMELINE (2020) + HIS BROTHER
This is the current timeline before Han Tae Sul invented the uploader, and when he saw his future photos with Seo Hae. The photos Han Tae Sul saw are from between 2020-2035, when he got married to time traveler Seo Hae. As for who took the photos, these could have been taken by his brother, who, as we all know, is still alive. Additionally, 9-year-old Seo Hae also lives in this timeline, while the 2035 Seo Hae travelled back to this timeline.
• TIMELINE #3: SEO HAE AND HAN TAE SUL FROM 2020 – 2035
Han Tae Sul invented something from his current present that led to mankind being able to travel back in time. The nuclear war probably happened when Han Tae Sul and Seo Hae were attacked during their wedding; the ones who attacked them could be the control bureau or Sigma. Sigma is already a time traveler from 2020-2035, but he went back to the past even earlier than 2020. Still, the people who attacked them could be anyone capable of traveling back in time.
All in all, the Control Bureau, Sigma, and the brokers got the ability to go back in time. Seo Hae will keep trying to save everyone, but getting attacked during her wedding will keep on triggering the nuclear war ending and creating the future of the child Seo Hae to grow up during the war — hence, once again creating the time travelling future of Seo Hae. (see graph for reference)
• MIXED TIMELINE: THE PAST AND PRESENT JUNG HYUN KI
There are two Jung Hyun Ki’s in Han Tae Sul’s current timeline: the one who got controlled by the Control Bureau, and the future Jung Hyun Ki who was already part of the Control Bureau but eventually left them after he learned the truth about his mother’s death. The present Jung Hyun Ki’s life got altered due to the Control Bureau, leading to the future Jung Hyun Ki to apologize to Seo Hae – who got framed for what the Control Bureau did – in advance.
CONCLUSION AND THEORIES:
In conclusion, 2035 Seo Hae at war’s timeline wouldn’t happen if there were no time travelers, since the nuclear war probably wouldn’t have taken place. Han Tae Sul’s timeline (being chased, etc.) is only happening due to time travelers, and time traveler Seo Hae knows what’s about to happen because that’s most likely her future self’s “past.” (refer to graph is you find this confusing) The wedding probably happened when she was able to save Han Tae Sul and time traveler Seo Hae eventually married him. However, in that same year, there’s another Seo Hae who is still a 9-year-old child. Hence, there are two Seo Hae’s in Han Tae Sul’s timeline: child Seo Hae in the present (whose life became the at-war Seo Hae destined to save Han Tae Sul) and the future Seo Hae who came to the past to save him and eventually marry him (due to the repetition from her future self).
Seo Hae’s mission is to try to stop the Control Bureau/Sigma and save everyone by traveling back to Han Tae Sul’s current timeline. But history keeps repeating itself, if she saves him there won’t be any war and they’ll get married between 2020-2035. If she doesn’t or they get attacked during the wedding, there will be war (between 2020-2035) and her child self (from 2020) will turn to war-Seo Hae (from 2035); the 2035 at-war Seo Hae will then travel back to 2020 again. History will then keep repeating until Seo Hae and Han Tae Sul saves the world.
What I dont understand is if time traveler Seo Hae managed to save Han Tae Sul and stopped him fron making the uploader, will she not exist or disappear by then? Since she is fron the future? And if there will be no time machine the time traveler Seo Hae would not exist right?