This is Yuri Nakamura, leader of this faction. She says her enemies are angels, but at first blush the person she's aiming at looks like a normal girl.
Our boy thinks she might not be a good guy.
He rebuffs the recruitment and tries with the alleged angel.
She denies being an angel and declares that she is the student body president. But she confirms that everyone here is dead.
Our boy concludes this is all a trick and challenges her to prove it.
She materializes a blade and runs him through.