For convenience, the character played by Ahn Jaehyun is referred to as "Ahn" and the character played by Seo Inguk is referred to as "Guk."
Note that this interpretation follows the opinion that the events in the video occur in chronological order.
-> Guk smoking a cigarette = the last event in the timeline
1. They reunite at a mutual acquaintance's funeral after 10 years.
They exchange phone numbers at Ahn's suggestion.
2. After reuniting, they often meet and reconnect.
-Guk learns that Ahn is divorced.
-Guk attempts to kiss Ahn while drunk.
3. For some reason, Ahn dies afterward.
*Up to this point is the first timeline = Guk's perspective in the teaser
Guk repeatedly goes back in time to save Ahn but fails.
*The broken clock
Guk's failed attempts to go back in time
No more options left
+There's a possibility that it was a trace from the accident since it's a keepsake of Ahn, who is deceased now
4. This time, Ahn knows that something has changed (Guk is surprised)
*Ahn (Blackberry) and Guk (iPhone) exchange numbers
From Guk's perspective, Ahn is a "being from the past" and Guk is a "being from the future," intersecting at a point.
5. They start reconnecting, and Guk feels brief happiness.
6. However, to avoid Ahn's death, Guk suppresses his emotions.
He doesn't attempt to kiss the sleeping Ahn.
Instead, he gives Ahn the watch that acts as a time-travel medium.
(Behind-the-scenes not shown in the MV)
7. Guk confesses his feelings in the tunnel.
8. However, as Guk returns upon Ahn's call,
He disappears in front of Ahn's eyes.
-> He vanishes instead of Ahn.
9. When Ahn comes to his senses, he finds himself at Guk's funeral.
The vanished Guk is now dead.
Ahn realizes the truth upon seeing the watch on Guk's wrist.
The intact clock - implies Ahn still has a chance or suggests that Ahn's accident was "undone."
10. This time, Ahn returns to the funeral where they reunited.
It's possible that Ahn also made several attempts to save Guk afterward.
11. Ahn knows everything but only watches Guk leave to save him.
-> The "present" that has vanished
12. Due to Ahn's return, Guk is in a reset state, knowing nothing.
Guk realizes Ahn was also at the funeral and smokes a cigarette, muttering "I missed you" in a low, murmuring voice
"There's no breakup song that suits me"
(NB: Literal translation of the song title)
Their meeting (reunion) itself has "vanished," making any breakup impossible.
The music video stars actors Seo Inguk and Ahn Jaehyun, who were the main characters in K.Will's 2012 music video "Please Don’t." The video gained attention with its bold setup of Seo Inguk's character having an unrequited love for his same-sex friend Ahn Jaehyun. Even 12 years later, the video is still discussed, and the two have earned the nickname "World Gay." This new music video tells the story 10 years after "Please Don’t," with an even more intense atmosphere.
Also, the timeline of this music video is set in 2022, two years prior to the "present."
*I'll add the comment left by Commenter #32:
This seems to be a story from two years ago since BlackBerry's service ended in 2022.