Tatsuro Daizo is a hacker and a document forger.
Daizo is an assistant of Root after she saved him from the Tokyo police. In Champaign, Illinois, he helped Billy Parsons create a fake ID of Gunter Schmitz, an employee at the Department of Defense who was visiting the National Center for Supercomputing Applications, a secure building which participated in developing a new computer chip. He was then told by Root to meet Daniel Casey at a safe house in Perth. (“Root Path (/)”)
They go to Reese's safe house where Root gives them instructions to make certain modifications to the Samaritan servers and also to find out the locations a tracking device Root pulled out from a car of a Decima operative to know where it had been. Root leaves them to their tasks.
Later, Root called them to get a status update and they stated there had been some complications with the servers but that the work is proceeding, also, that they had been unsuccessful in retrieving data from the tracker. At some point, Root uploaded data from a USB drive retrieved from a Vigilance operative which contained a Stuxnet based virus and tasked them with finding its target. When they discover the intended target was the power company they promptly called Root providing her with the information.
With the servers ready and after getting a location from the tracking device, they travelled to a facility where a part of Samaritan was being stored. Root gives each of them an envelope with new identities and told them a car would take them where they needed to go. (“A House Divided”)
Daizo's new identity is one of the seven created by Root and hard coded in the servers for Samaritan to ignore as Root considers him one of the seven people capable of taking the world back from Samaritan. (“Deus Ex Machina”)
Daizo's first name was revealed to be Tatsuro in “SNAFU”.