Job is not asking a question about justification in the sense that Paul does in Galatians or Romans. Though one wished to dispute with him, He could not answer him one time out of a thousand. God seems unfair. That's Job's despair. His world-view is coming apart.
Life makes no sense.
He cannot get a handle on his world. The suspicion is growing that God's providence is inherently unjust. Job feels trapped. He can see no way of escape. There is a hopelessness about his condition that throws him into the darkest despair.