Significance Collective cell migration is an important phenomenon in the developmental process of living organisms and even in mature individuals. The cells in the collective are accurately classified into leader cells, which lead the collective at the leading edge, and follower cells. We found that in the collective migration of keratocytes, the epidermal cells of fish responsible for wound repair, a mechanical interaction between two leader cells and a single follower cell can forcibly break the connection between the two leader cells and transform the follower cell into a leader cell.