Isako was the leader of the Katakuri Ninja Clan that operated out of Inotakimura, Japan. She and her clan serves as killers for The Director and H.A.R.M., primarily out of duty than a sense of allegiance. The Director has stated to dinner guests that he must manipulate Isako much like a little dog (much to the anger of some of the clan members) but also recognizes her honor and competence in his happy birthday note he wrote to her (as later found by Cate Archer).