Immediately follow the prompt to drop a Smoke Bomb. This will give you the initial time to start running. Turn to the West and start up the wall. Bellec will be setting a good pace throughout this run.
At the top of the wall, cut across the roof for the one open window. Go through the building and then follow Bellec as he leads you out of the area. Right at the end, you will come across 2 Guards. Bellec will prompt you to throw a Smoke Bomb. Just follow the onscreen instructions and it is very simple to complete.
Now just keep up with Bellec he will take you up and over the rooftops. Just stay with him as best you can. If he goes into a building, it is generally a bit easier to go over it. Just keep up with his overall pace and you will have little trouble.