One thing the drama does well is show FCY's care for XZ. Her care and protection of him really touch him, an orphan abandoned by his mother and used by his uncle.
Ep.25: I'm not sure why the people who know XZ are asking him about the reason he concealed his identity from FCY. The reasons should be obvious to them. Commoners may be ignorant but not a person who is aware of court politics and an imperial princess.