C517

Because of Ye Xiu's promise, coupled with the fact that Ling Zhen did not want to be held back by his Five Elements' Sect, in the end, he still agreed to Ye Xiu's departure.

As for the reason, it was very simple. If the first and last instruction were to be fulfilled one by one, then even if Ye Xiu never left the Five Elements' Sect, the teachings of the ancestor would still be realized