Responses
Commenting bc I'm interested.
http://www.mangago.zone/read-manga/a_way_to_protect_you_sweetheart/
This may be something similar but the fl has a curse, not illness (￣∇￣")
Were fl has a limited time to live or is very sick.
(They don't have to actually be sick or die kinda like http://www.mangago.zone/read-manga/when_the_villainess_loves/ or http://www.mangago.zone/read-manga/happy_ending_for_the_time_limited_villainess/)