According to Sword Saint, the reasons why the three became Mr. Du's disciples were really simple. In reality, however, there were much more hidden behind the simpleness.
Sword Saint did not tell Ye Futian that in order to carve something onto the stone wall that time, he did not sleep for three months. His sword-yielding hand was rubbed to bleeding. He fell down countless times but stood up every time. Finally, he succeeded but was still chased out, after which he lost consciousness. Mr. Du was beside him and watched him for three entire months. When Sword Saint fainted due to starvation and then woke up, Mr. Du gave him a few fruits. That was why he would live to become the eldest disciple of the Cottage in the first place.