That sword can change what happened in the past and then influence the present. The feather flied back to many…
In the old timeline, the Clinic had three workers including Cui's husband, and Xuanye later killed 6 person(father, mother, brother, three workers).After that accident, Xuanye felt guilty and took care of lady Cui in daily life. They are colse contacts . In the new timeline, the Clinic only had two workers and Xunaye killed 5 person(Cui mentions that). Lady Cui only views Xuanye as a neibor and doesn't know Banxia.
what happened after white crow was killed , why xuanyue dont remember he used the sword to kill the white crow…
That sword can change what happened in the past and then influence the present. The feather flied back to many years ago when the lady and her husband passed by the Clinic and make the Clinic's job recruitment board fell. In the original timeline, her husband saw the notice and then be employed by Ganshan clinic. But in the changed the new timeline, lady Cui's husband didn't see the job notice and became a blacksmith, so everything happened later about her changed . ML and FL's memories are also changed and do not have memory about white crow now.