Taking advantage of the target's attention on the weapon in hand, the user drops their current weapon and quickly claps their hands together in front of their target's face; because the target was so intensely focused on the in-hand weapon, the clap will momentarily stun them.

What is Nagisa's gender?

Nagisa teaches him that he can turn his weaknesses into strength and also reveals that he is male, to Yuji's shock.

What did Nagisa do to Takaoka?

Nagisa then lets the knife drop, which distracts Takaoka and fakes him out with a sudden loud clap. At this, Takaoka is momentarily stunned, allowing Nagisa to close the gap and use the stun rod to electrocute Takaoka into submission.