Looks like duty never ends but it started with a person, who was the empress.
As far as I grasp from the story, the empress has difficulties and until those ends, she will be near the empress. In fact, when the empress almost demonstrated she could be by herself pretty fine, the FL's health started to deteriorate cause she couldn't stand the thought of being "not needed" anymore.
These are my thoughts and I see some stuff i am not sure about so... (￣∇￣")
Its really complicated this kind of duty they had you never how it end co'z of third party will join to wreak their duty or not.
Yes, you're right. I think it could be great if they explain the concept better, cause the story goes around it.
Himm does duty end? Coz the way she said its like for lifetime eh.. she scared of bein abandon.. i hope there a way to not cause a duty so she can be with her highness and the crown prince lmao.