Warning: the first blue box appears at chapter 24. David always lived his life, looking at the world through a film of grey. He knew he was dull, he knew he was worthless. And the world was too. His life ended in an instant, hit by a truck. Then he woke up again, and the System gave him a mission. Pretty standard isekai, so far. The only problem was that whenever he died, he respawned. After agony and pain, he would come back reforged. And so he died, again and again. And when he completed his mission, another one awaited. On and on.  But his life had meaning now.