(Trigger Warning! Don't like, don't read!)
Everyone knows that you wake up from the simulation after you die in Danganronpa. So why is Rantaro called the Ultimate Survivor? Because he was the only to make through rehab and therapy. Everyone else either died because of a sickness the game gave them, killed themselves, or just died from stress. Amami only kept going because he wanted his fellow classmates live on through him.