"Things a Northern Grand Duke in a RoFan should not do:

Seducing the Female Lead, tossing the territory aside, and playing around in the Capital.

Being cold to other people but sweet only to the Female Lead.

Being deceived by the Female Lead's sweet words to start a rebellion and become Emperor.

Things a Northern Grand Duke in a RoFan must do:

Grinding one's own martial arts to become a Sword Master.

Introducing a modern General Staff Headquarters system.

Constructing a standing army before the monsters beyond the barrier attack."