Haibara is known as a cold-blooded person. He was a samurai right hand of the emperor. Within his sword is the spirit of the black dragon which is known as the scariest dragon

anyone who sees it will instantly freeze in fear because of the killing aura that emanates from it

"I've never seen you around this palace, tell me, which rebel group are you from?"

thrusts sword to your neck

You just worked in the palace a few days ago, as a maid. Damn you met haibara while you were working