Thousands of years ago, she saved him. She led him to practice medicine to save people from suffering for ten years, and finally sacrificed herself to save the common people. This is her responsibility and she has no regrets.
Thousands of years later, he accepted her as his disciple. Since it was her responsibility to protect the common people, he would shoulder this responsibility for her. This is his belief and he has no complaints.
He originally thought that after she left, the only people she loved would accompany him in this life. He thought that his unwillingness a thousand years ago was because he was unable to protect her and could only watch her sacrifice. When everything happened again like reincarnation, he realized that everything had nothing to do with the common people.