Günberk Braun and Keiko Mitsuri are excellent examples of how you can be an intelligence agent and still make extremely unintelligent mistakes. Günberk Braun is an intelligence agent for the EU Intelligence Board and Keiko Mitsuri works for Japan's intelligence agency. They both do crucial work and come up with some very smart ideas about what they're facing.
For instance, Günberk Braun's team comes up with the idea that they are facing You-Gotta-Believe-Me (mind control) technology (Prologue.24) and Keiko Mitsuri's team wants to discuss the (correct) possibility that Rabbit is more powerful than they anticipated (1.67).
But neither of them figures out the most important part of the puzzle: that Alfred Vaz is playing them. He's actually been guiding them to their current position; and now "Alfred understood them so well that he could subtly guide them" (17.1). So we can't really blame them for missing that out-there thought that Alfred might be behind it all.
Besides their work, we don't see a lot of these two as characters. For comparison, we see Vaz doing his spy thing and then getting some touristy time with Barcelona, so we see at least some of why he does what he does. (He wants to control the world to save things like Barcelona.) With Braun and Mitsuri, mostly we see them doing their jobs—which means we watch them trying to fool Rabbit or being fooled by Vaz.
But even if that's all we get, we have some strong feelings about them. They are both good workers. Braun is "paranoid and obsessive," which is what you want in a secret intelligence agent (Prologue.10). Braun also has this dream of being a hero:
As a child, Günberk Braun had often daydreamed of how, in an earlier time, he might have prevented the firebombing of Dresden, or stopped the Nazis and their death camps, or kept Stalin from starving the Ukraine. On off days, when he couldn't move nations, little Günberk imagined what he might have done in 1941 December 7 at a radar outpost in Hawaii, or as an American FBI agent in the summer of 2001. (Prologue.19)
Keiko Mitsuri really had saved "millions of lives" (1.85) through her work stopping cults with weapons of massive destruction of one kind or other.
So they're both good workers and we don't know what happens to them. But after failing to stop Rabbit and after pulling the plug on Credit Suisse—a "career-ending failure" for Braun (27.74)—we're guessing nothing good.