Yang Zhen did not like owing favors to others, especially to Saintess Tianxuan whom he had met only once. For some reason, as he listened to the story up to this point, Yang Zhen really wanted to repay this favor.
Actually, the reason Yang Zhen had achieved his current success was largely because he had once witnessed that sword strike from Saintess Tianxuan. Otherwise, even if he could have made a breakthrough, he would have been just a Half-step Great Saint, not skipping that level entirely in the Annihilation Heavenly Sky Lotus and breaking through directly to the Saint Realm.
Yang Zhen did not know whether Saintess Tianxuan would have swung that sword if someone else had entered the Nine Realms Exquisite Tower, but he knew that it was him who had entered the tower, and it was him who had that fleeting encounter with Saintess Tianxuan.
That was enough!