Clacier is expelled and joins the rebel group "El Dorado" to overthrow the government.

Clacier (an orphan magic sword user) and Annette (the top graduate of the knight academy) begin as close friends and comrades in the Special Forces.

To understand the DLC, it helps to know the base story it expands:

It further explores the moral ambiguity of the Kingdom of Viktor and the differing philosophies of the knights. Core Narrative Context

The "Ideology in Friction Append" DLC expands the original dark fantasy story of elven knights and Annette Stole . This expansion is most notable for adding an entirely new story chapter centered on Sachiyo , the strongest of the Viktor Knights known as the "Samurai," and her first encounter with Zepp . New Story Content

Reviewers note that the DLC significantly increases replay value by adding more variation and immersion to these existing routes.

Because it adds to the main story, players typically need to replay or load saves from specific points to see the new DLC-exclusive scenes and the Sachiyo chapter. Ideology in Friction (Video Game) - TV Tropes