This scene comes from the episode Lelouch, Friend or Foe in the Aaron's Adventures Chronicles
Zero: Well, now let's end this nonsense once and for all.
???: I agree, but, not like you planned it, Zero.
Aaron: No way, I know that voice.
(Soon, the mysterious voice jumps down to reveal Tetsuo Xenon)
Jake: Tetsuo Xenon!
Zero: And you are who?
Tetsuo: I am Tetsuo Xenon! And I have discovered your true identity.
Tetsuo: Then let's get a better look, behind that mask!
(As Tetsuo removes Zero's mask, the whole gang discovers the truth of this black knight.)
Tetsuo: I knew, it was you.
Aaron: So that's it, isn't that right, Lelouch!
Lelouch: Yes, I am Zero, the man that you met once before, the who holds the entire world in his hands.
Tetsuo: Not this time, Lelouch.
Lelouch: Really? How's That?
Tetsuo: You'll find out now.