Alright, that's a wrap.
So I know most of you are confused, so here's a basic run-down.
At the start and end of the story, Thorn is always presented with Where are they?/How long has it been?/I don't know loop. This is because:
Thorn wants to know where his friends are.
But does he not see all of them in different occasions? Yes, he does!
From how long has it been/I don't know loop, we can tell that they have lost sense of time.
Thorn keeps asking where are they? despite his friends being right in front of him is because:
They aren't his friends.
That's why he keeps asking them the same question. So they must be something hollow, empty, and robotic. We can see this through their speeches.
Cyclone said: "I've planned a wonderful game."
Blaze said: "It's an unsightly place."
From this alone, we can know that they would never say that because of their personalities. This means the people Thorn is seeing isn't his friends at all.
And at every ending scene, where everything always turns barren and withered. Cyclone's cap drops from a tree. Thunderstorm's swords pierces through two jackets, red and yellow. Quake's house is destroyed, the picture frame falling. (Etc, etc)
It always means death or abandonment.
And as for their behaviour towards Thorn, it can be seen in their personalities too. Cyclone is cheery and welcoming. Quake is somewhat close and can touch Thorn. Thunderstorm is hostile and doesn't let Thorn come close, has a strong barrier. Solar can touch Thorn in whole, even hug him and feel his weight.
This is how Thorn remembers them. Specially noted ones include how Thorn first meets them:
Cyclone is sitting high on a playground equipment, and Thorn can barely see his silhouette.
This means Thorn in this universe isn't close to Cyclone.
Quake can touch Thorn's hair.
They're close, but Quake is remembered in a maternal sense.
Thunderstorm's lightning blades harms Thorn.
Thorn remembers Thunderstorm as hostile and unapproachable.
Ice lets Thorn come close, but they don't talk.
They have a mutual relationship.
Blaze's voice is clear but they're far apart.
Thorn in this universe has a vivid image of Blaze, but his personality isn't understood by Thorn.
Solar can hug him directly.
They're very close, but not romantically.
And at the final chapter, Solar is gone right in front of Thorn's eyes. There's a sentence that says he can't get the answers he wanted.
So, what does this mean?
He can't get the answers he wanted.
He asks all around, but they all don't know. Thorn doesn't know either, always replying I don't know.
It also says in this barren world. It means the world he knows is gone. He's waiting for something in a dead world.
Waiting for what?
In the epilogue, it says, "why do you not see truth, Thorn?"
He sees Solar disappear in front of him. He sees the other elementals hollow. But Solar looks alive, because they're close. Thorn remembers every part of Solar, so that makes him more alive than others.
This means that Thorn's been seeing nothing but his own fragments of imagination! Or rather, memory of his friends.
The other six have died and passed on, but Thorn stubbornly remains, asking himself where they were. They were nothing but his memories. When he doesn't get the answer he wants, he looks for someone else.
Note that the other six are found where Thorn remembers them to be most. (Solar in a lab, Thunderstorm out and alone, Quake in the house, Blaze in the sewers so he can't do harm, Cyclone in the playground, Ice at the cocoa stand).
Thorn died as well.
This is why he could survive in that barren world. It doesn't affect him, because he's already dead. Thorn is stubborn and overly optimistic, so he refuses to believe they all died. So he keeps looking.
How did they die?
There's a mention of wars. There was only one war where the entire elementals were involved. Every element that has a chance of death.
The battle against Retakka.
They lost against him, and Retakka has managed to steal the resources on Earth. Thorn is a lingering spirit who refuses to come to terms to his own death, and keeps looking for his friends.
The memory, the phantoms of his friends always as him, How long has it been, Thorn? Because they were his subconscious. He himself wanted to wake up, to accept reality. But he didn't want to.
Note the emphasis on his name. Thorn at the end.
That's all :D