The Next scene is V waiting for Jin. Notice the picture he crumbles up in his hand, it's a picture of a man holding a child. From this we assume that the man in the picture is the man V killed (V's dad). All the members (except for Jin) show up and help him up, notice how he doesn't hug any of them, but when Jin shows up (with his camcorder) he hugs him almost immediately. "You can smile as long as we are together" shows. The small things to take note of in this scene are...
1.) The car Rapmon hits into the puddle with a stick
2.) Jin recording everything
3.) J hope sleeping. Kookie and Suga wake him up.
4.) V standing by himself atop what looks like an abandoned building or just some sort of higher ground, away from the rest of the members.
Next Scene Rapmon writing "You need to survive". We take this as a message to V and Jin (and possibly Rapmon). If you haven't already remembered, now is the time to remember that in the I Need U M/V all of the members (except V, Jin, and Rapmon) committed some sort of suicide. I'll explain later why I think Rapmon didn't commit suicide.
Next scene they are around a fire, watching footage that Jin caught on his camera. Notice Suga hazily looking into the fire while flicking his lighter (think about the beginning of I Need U when he's flicking his lighter) Jin pulls out a photo of what is the last screenshot at the end of I Need U. It's of an ocean. He asks the members, "Should we go here?". Notice how none of them actually respond with words. Notice Jimin's expression. He's obviously sad but slightly smiles. As if he knows something will happen that we don't know. Notice Kookie blowing out the lighter. (I'll explain why that is important later)
Next scene. They go to the ocean and have fun. The biggest thing to notice is Jin's obsession with capturing everything.
Next Scene. The gas station where Rapmon worked in I Need U. Rapmon asks Jin for the camera to take a picture. Rapmon takes a picture of Jin and Suga. He places it in the glove compartment of the car. The scene with J-Hope and Jimin. J-Hope comes walking out with food, notices Jimin asleep (important) and covers him up with a blanket to keep him warm (also important, I'll explain later)
Next scene. Kookie looking out at the ocean, he looks solemn. Suga comes over and seems to cheer him up a little, it seems as if they know something is going to happen. They all wake up and chill on the pier and V looks up at this tower thing with a frown, pulls his hood up and climbs the tower. Jin seems to be clueless, while the other members haven't seen, or are not paying any mind to what is going on. Once at the top the members look up at silhouetted V and motion him to come down.V smiles at his members, and with a serious face jumps off of the tower, thus ending his life. If you look it seems as if some of the members put their hands out in response to his jump like "No stop don't do it."
Ending scene. The biggest thing to notice here (and a lot of people didn't notice) is Jin is in his car by himself and it is going underwater. His car is completely tilted forward and the water level compared to his car shows that his car is sinking into the ocean while this scene plays out. There's water on the windshield and on the sides of his car and windows. The biggest piece of evidence is in the beginning of this Rapmon hits a toy car into a big puddle. Jin pulls out the photo from the glovebox, where it was suppose to be of him and Suga, it's only him. This explains that J-Hope, Jimin, Suga, and Kookie in this were all figments of V, Jin and Rapmon's imagination. Jin goes from smiling to frowning, the camera blurs and it's the end.
Now the reason why I said J-Hope sleeping (in the beginning) and Jimin sleeping were important things is a story in itself. Because the other members are ghosts (dead) they are comforting each other, because they can. They are part of the afterlife. They are together in the afterlife. J-Hope sleeping while everyone else is having fun (he OD'ed on pills, passed out on the bridge in I Need U) Suga and Kookie wake him up. Suga hazily looking into the fire while flicking his lighter (he sets his room on fire with gasoline and his lighter) Kookie blows it out. J-hope covering a cold and sleeping Jimin, (Jimin drowns himself, in the I Need U M/V he's seen shivering)
The importance of "You can smile as long as we are together" is that Jin and V were holding on because of the illusions of their now passed friends. Because they still saw them, they technically were still together and could still smile. By the end of the trip both V and Jin come to the conclusion that it's all illusions and can no longer smile, because they are in fact not together anymore. V suicides first and then Jin. Jin in the end confirming that it's all just illusions with the picture while in the process of being in his sinking car.
LASTLY (I know this is long I'm sorry but it feels good writing it all out to have in front of me and anyone else reading my theory) I think Rapmon didn't die in I Need U. Yeah, the lollipop represents a cig and he drops it at a gas station, but that doesn't mean the place blew up. People drop cigs at gas stations all the time. This prologue helps confirm that he didn't die. Rapmon took the picture of Jin and Suga, if he was an illusion, that couldn't have happened. I think the whole "You need to survive" is Rapmon telling himself that (possibly a forward shadowing) after Jin and V suicide.
So that's my take on it all. And then Rapmon ends up in a mental institution (Joke M/V) AMIRIGHTORAMIRIGHT? Lol that last part was a joke but yeah. If you took the time to read this, thanks.
EDIT: After reviewing comments, it seems as if Rapmon not being alive makes more sense. Especially Mako's comment, if you do look closely to the left in the picture you see Jin holding the camera himself. OH MY GOD THE FEELS ARE KILLING ME GUYS THIS TRAILER IS NO JOKE. So this makes me revise my theory (just a little).
Revision: Rapmon wrote "You need to survive" as a message to Jin and V, letting them both know that the two of them can only survive as long as they have each other, in the end V couldn't hold on, so he killed himself. Because Jin no longer has V, he followed suit.
Addition: So being that technically this was a V and Jin trip it was kind of a sad journey. They are all having fun in these places, but the other members are not real. In the scene where all the members meet up for the first time, and V is standing alone, you can tell he's contemplating suicide. When Jin asks "Should we go here?" It's like he's asking the illusions "Is this where we should end this?" because of you think about it, the photo of the ocean he pulls out is an old photo. It's a photo from the end of I Need U. It's a photo of a place they all went to when they were all still alive. A place where actual memories happened. Jin purposefully went back there with V while mentally unstable, recording false memories and taking false pictures to a place (maybe even the last place) they were all together before they all died and Jin felt like this was the only acceptable place to finish it all.