As a public servant, it's my job to serve the needs of the people.
Hart is the Deputy Mayor of Midgar under Mayor Domino. He can be found standing outside of the Mayor's office on the 62nd floor of the Shinra Headquarters. Hart is able to assist the player when they are trying to figure out the Mayor's password to get the keycards for higher floors; the more he is paid, the more help he will give. If the player will pay him enough, he will actually just tell the password.
In Final Fantasy VII Remake, his role is expanded, where he'll meet Cloud and his party and take them to see Mayor Domino, who reveals he is a sympathizer to Avalanche's cause. After the Domino tells the party to look for a Shinra employee that will give them the keycard to the 64th floor, Hart can offer to give a hint on the employee for 10.000 gil; if paid, he'll provide a very vague clue, but will also reward the party with EKG Cannon, a weapon for Barret.
Hart's Japanese name can also be translated as "Hut", a reference to the pizza chain, Pizza Hut. The mayor, Domino, is also a reference to a pizza chain, Domino's Pizza. Both names are an allusion to the fact that the city of Midgar is sometimes referred to as a pizza.