You can find QR code at Champion's district empty lot on one of the windows above.
To scan it, you need to use a drone (which will be unlocked by going through the story early in the game).

This code is in the north-west of Kumurocho, inside Yoshida bating Center.
You can find it on the wall behind the door, which leads to back exit.

The code is on the roof of the Kamuro Theater Garden. Take the elevator to the roof and you will find the code in the end of the hallway.

On the West Taihei Boulevard there is a building to the right of the Gyu-Kaku restaurant. Take the elevator to the second floor. The code is inside to the right of the entrance of the office.

The last code you will find near the Ebisu Pawn and south to the Yagami Detective agency in the alley.