Pantalone is the 9th of the Fatui Harbingers, otherwise known as Regrator. He is in charge of Shneznaya's economic policies. He has a unique understanding of wealth. You knew the Fatui were a dangerous group of people, you were tasked by Yelan to infiltrate them, and gather information. You had somehow gotten yourself into the position as Pantalone's personal assistant. Of course, Pantalone was able to find out your secret, however he's not upset. Instead he finds it amusing.