Edit: I'm at the end of the game and I have *no idea* what's going on, or what the story is about. Maybe it's the partial translation but nothing makes any sense at all to me.
Basically, it starts out with your just helping out around the clan, fighting off the normal enemies that threaten the clan, until one day, and imperial squad of Choppers come, destroying your village, and in turn, you entire clan. You are captured and put to work in an arena under the gimmick of being the last Gasar or whatever the hell that family is called.
You eventually fight your way to freedom in the arenas, and thanks to some guy who is an old friend of your family, take revenge on the destroyers of your clan, but they weren't the only ones involved, the emperor was a part of it too, so your fight your way through the imperial games, and once you kill the champion, challenge the emperor, you kill him and get revenge, but you get arrested by (what I presume is) his adviser, who was actually behind this the whole time.
He offers you the chance to help him kill the true evil, the machines (I dont know exactly what they were called) because they will soon rise up and destroy man or something along those lines. You accept (or dont, and have the most annoying battle I played) and descend into the rift, battle through robots and fortresses, finally reaching the mind of the robots, a sentient robot who is very god-like in his knowledge, you denounce him for toying with man, and fight him to the death.
After killing him you are left with nowhere to go, and out of supplies, without hope of reaching the surface before you die. I assume that's where he narrated his story to the player.