They were retreating.

They were running away.

The distance between the ones who were retreating and the ones who were moving forward seemed to be kept the same, which was within a few hundred meters. They didn't get too far away or too close to each other.

It was still the endless forest ahead. Under the dim setting sun, the scattered shadows of the trees were on the ground, dim and vague, but it was already a desert of yellow sand behind them. ...