Waddup ARMYsss!! Here i have compilations of theories/explanations about the BTS' storyline that you all have been cracking your heads off about.
I dont know if this whole theory is true or not but it seems like it is.
Also this theory is quite conf...
They all sit down by the pier and watch the sun rise: it's a new day, and possibly the start of a new life; V takes a look around and silently decides that it's probably a good time to part ways with his youth. Resolved, he puts his black hood on (a symbol for adulthood throughout the HYYH cycle), just like he did at the start of I NEED U. He climbs up on top of the large pontoon towering them and overviewing the wide, open sea of the unknown. Jin just watches V silently, recording the scene as he did before at the pool site. This is also a reenactment from the last scene in I NEED U.
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Prologue & INU (mirroring scenes)
The rest of the boys, stunned and scared, try to tell V to come down but he just softly smiles back at them as if not to worry. He looks anxious nonetheless, but eventually finds the courage to do what he's been set on doing all along. He then jumps off the platform, and into the sea while the Butterfly song plays in the background.
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Prologue (jumping off into the unknown scene)
The Prologue started at the pool site with V symbolically killing his father by creasing the picture of them together while V was still a toddler. But V was not ready just yet to leave youth behind and accept the consequences of his actions, hence why we see him pondering over what to do next while looking over the horizon from the diving platform (should he jump into the unknown, or should he stay safe in youth?). He then keeps revisiting his youth during the whole Prologue, coming to terms little by little with what he has (or had) to do and trying to find the strength to leave it all behind. By the end of the Prologue, he feels he is ready now to jump into adulthood for good, and so he does.
As the main entity, Jin does not interfere, but the boys, the other components of Jin's psyche, are not so sure about the bold and sudden move. V has set things in motion, but not all parts of Jin's soul were ready to be thrown into the unknown and to be transitioning to adulthood just yet (as mentioned before, it's all part of a process Jin has to go through in his mind to reconcile what he once was with what he is now). The whole HYYH Trilogy is about all of them coming to terms with the end of youth, so they can all move on together to the next stage of life (Jin's life). Until then, they won't be able to break the cycle.
WAKING UP
During the end credits, the song "Je ne regrette rien" by Edith Piaf is playing. In the Inception movie, it is played every time as a wake-up song for people involved in a common dream, to tell them the effect of the sedative will soon end and that they will wake up. It is played here at the end of the Prologue with the same intention to wake the boys up from their shared dream. Both in the movie and the Prologue MV, the message behind the song is clear, and hopeful too: "Do not regret anything" (and move on).
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Prologue (waterfront & car motif)
After the end credits, we see Jin by himself, in his car (symbol of adulthood), still by the shore (in between 2 states). He then takes a look at a polaroid picture of him and Suga that Rapmon had taken earlier. Visibly puzzled, he can only see himself: this is because Jin is out of the dream now, and the boys simply don't exist in this realm.
