In episode 17 of Code Geass: Lelouch of the Rebellion R2, there's a song playing when Lelouch and Suzaku met for the third time. (YouTube link).
What is that song?
It's called Declaration of War, allegedly an unreleased OST. I found it on youtube by side while going through Code Geass tracks researching for another song, and I remembered it when I heard it in the video you linked to. It is somewhat similar to Naruto's Orochumaru theme.