I think the time starts from the first bar segment.

Fast forward through all of the text, as quickly as you can, when you get to Lady's apartment, beeline for Starlight, the first part is fairly straightforward.

Once you get to Justice, turn around, open the door and immediately turn back around and start the trial. I wasn't able to get the trial to start without opening the door.

It doesn't matter who you accuse in the trial, just mash through.

I had about 7 minutes on the clock by the time the trial was finished.

Now, exit the courtroom and jump over the balustrade/railing to your left. Jump over the rocks and when you get to the alleys, this is where it gets a little tricky.

What I found the most effective was to veer right, jumping onto some air conditioning plant, and over the bridge past the footbath. My attempts lost the most time in the canal.

On the other side of the canal head left and take the right pathway over Crimson's hidey hole.

I got caught next to the stairs onto the promenade but i had enough time to make it to Lydia and fast forward through the end text.

I finished with 9 minutes on the clock, and the achievement popped as soon as the credits started rolling.

What is going to kill your time here is your routing from Justice to Lydia in the epilogue. Be careful with your jumps and you'll be fine.