Ok so I beat the game finally and I'm going to have lots of spoilers.
The World ends With you is a very intresting game and the main themes of the game are about people and their relationships with others as well as individulaity. Shibuya is represented as a place that has all kinds of ideas and different people. It's a place of indivuality and self expression. But none the less every person is an island encompassing their own world. And Neku Sakuraba is someone whose world extends no furthur then himself. When the game opens you see him walking along alone saying he doesn't need anyone that the only one needed in this world is himself. He's just a self-centered lonely kid who has no one who understands him and he doesn't even try to understand anyone else. He doesn't trust anyone. He doesn't even care.
As the game progresses though you see the Amnesiac Neku changing. The first one to start this change is Shiki, his first partner. At first he treats her like shes just some stalker who is annoying him. In fact when one of the reapers tells him they will let him out of the game if he kills her or he will get erased himself he decides its her or him. Luckily My Hanekoma comes and stops this saying its against the rules. Hanekoma tells him he needs to trust his partner. After that Neku starts to change. Neku is not a bad person really so he has a conscience. Realizing that what he did was wrong he makes up with shiki and starts to open his heart up as Shiki's past is revealed.
Shiki herself had expeienced betrayal in friendship and she was jealous of her friend. Before she died her friend had told her she had no future in design. This really hurt Shiki, it was her dream to be a designer like her friend Eri. But then it turns out that Eri was only trying to tell her that she was talented with sewing that she had the ability to bring the designs to life. As Shiki heals her heart of her jealousy and realizes that Eri was only pointing out her true talent Shiki is also helping Neku.
In fact she becomes so important to him that when he gets put back into the game after the 7th day she becomes his entrence fee. This shows that his world has expanded that no longer is he only caring about himself. So now he's fighting for not only his life but Shiki's life.
Hanekoma is an intresting charachter. He is actually the artist CAT who Neku admires though you don't learn that till later in the game. His advice to Neku makes him think. he tells Neku enjoy the moment. Expand your world. Trust your partner. He helps Neku see that the world ends with you however in order to expand your world you need to reach out to others. You can't fully understand anyone but you can try and in doing so your world expands. Hanekoma is like a guide to Neku.
Another charachter who helps Neku Grow is Beat. Beat who was partnered with his sister initially is very simple minded. He ends up becoming a reaper but in the 3rd round becomes a player again to help Neku when no other players are in the game but Neku. Beat feels bad about causing his sisters death and wants to change her fate. And even though he hated Neku at first as neku changed they become friends.
His secong partner was Joshua, a secretive and sly charatcher who seems very untrustworthy. A guy who says he wants to jack Shibuya. Someone who doesn't seem like a normal player. Someone who it turns out even killed Neku. Neku suspects him at first but then is convinced that the Reaper Minamimoto was the one who killed him. In fact he even makes neku think he died to save him on the 7th day as partners. However, this is all a trick. Joshua who is rally the Composer tricks Neku and makes him feel like he's found someone who understand him. Even though he's changed himself and no longer felt like you don't need other people he still feels like he's found a friend. It was all a game between the Conductor and the composer. Neku was killed by Joshua to be his representative.
Neku who had not trusted anyone who had shut himself off from the world had finally opened his heart up to others and seen their value. The truth was he was being used by the Composer. He was murdered and made to suffer all for a bet. In the end Neku is the one who is hurt. To trust only to be betrayed by someone he thought was his friend. In the end Beat, Rhyme, neku and Shiki get their lives back. But Neku has a new scar in his heart. His last lines are I won't forgive you. but i trust you. And now I'm not alone anymore I have friends. Even though he was lied to and betrayed he's much stonger then he was because he's learned to trust others. He has people to support him. Even though he's been betrayed he chooses to still believe that Joshua will allow Shibuya to continue with its cacaphony or ideas with its clashes and battles to be the most fashionable. So it's not really a tragedy becasue Neku is transformed into a better person. In fact Shiki, Beat and Neku are all three transformed. The problems that were plauging them before are all delt with in the UG just by working them out together.