"A leader chooses a deputy. A deputy just has to be any warrior who has mentored at least one apprentice. If the deputy dies, a new one must be appointed before moonhigh that same day. Then when the leader loses their ninth life, the deputy becomes leader. Of course, if the deputy and the leader died at the same time, there would be some confusion¹, but that hasn't happened in my memory. Sometimes leaders do choose their own kits, but not always." Mothwing pauses. "Wait, why the eldest son and not the eldest kit regardless of gender?"

¹Definitely not the plot of the Warriors arc Mothwing was pulled from right before.