@huttingham
Actually, the term really is realism. The problem is that it's not well-explained here what realism
means -- honestly, it'd only really make sense at face value to people who study political science and international relations.
Given the premise of the story, the villain/anti-hero/protagonist's use of the term realism refers to IR Realism, a school of thought in international relations that calls for the supremacy of the state's interests over any alliances or the security and integrity of other states. It posits that states exist in a state of perpetual, global anarchy in which every state is naturally inclined to compete with each other for resources and power as a means of preserving its own existence. To that end, realists argue, it is not only morally acceptable but morally
necessary to do whatever it takes to ensure the nation's survival, even if it means breaking alliances and international law, allying with horrible people, bullying weaker nations, etc.
Thus, when the protagonist says that it's about trickery, subterfuge, etc., that's what he means -- that realism calls for maximizing the power of your state at the expense of others by any means necessary, no matter how morally questionable it might seem, because the ultimate goal of national self-preservation trumps all other considerations.
To be fair, though, I honestly haven't seen many (if any) manga that have made Realism particularly clear. Even Realist Hero kinda fudges on the details of IR Realism and it's the entire premise of that story, though at least it shows that you can be an IR realist and yet be a soft-hearted teddy bear domestically.
To be honest, my biggest beef with this chapter is the fact that the maid claims he's like Liu Bei, even though his dialogue might've been ripped right from the mouth of Cao Cao, who was a
far better example of realism than Liu Bei ever was.