have seen similar set-ups before. both don't want romance and set up the engagement on that basis, typically to make it easy to cut off if one side suddenly changes and tries to make use of the relationship to go overboard. also pretty typical for the agreement to be annulled or adjusted when both people end up realising they fell in love with the other and have to go through a bunch of drama, trouble and misunderstanding to resolve it ahahaha.
the benefit of this currently just being a verbal agreement is they have the flexibility to change the terms without much issue later if they agree on it.
as such my curiosity for this series is less on the romance potential between them and more on what that annoying princess with do going forward, she clearly has a great dislike of our main girl.