He is Lelouch's childhood friend-who became his biggest enemy.
He was given the title of Knight the Seventh, one of the knights under the direct command of the Emperor, due to his achievement in capturing Zero during the Black Rebellion.
His almost superhuman combat skills are so strong that his presence alone can turn a battle situation.
He was cornered during the battle with the Guren S.E.I.T.E.N. Eight Elements, and launched the F.L.E.I.J.A., destroying the Tokyo Settlements. After losing everything, standing at ground zero, he reached an important decision. He received an order from Schneizel, and left to assassinate the Emperor of Britannia. However, he lost to the strongest Knight, Knight the First, and he barely escaped death, thanks to Lelouch. The Emperor is killed by Lelouch in C's World, Suzaku faces his best friend, and then...
When Suzaku next reappeared to the world, he was the 99th Emperor of Britannia's Knight, Lelouch's Knight... Knight the Zero.