I believe I must be missing a step or prerequsite as I am running around Midorl bridge in Mor Ardain upper level at 16:00-18:00 with Kagas equipped as the "first blade" on his driver to no avail. I don't see the trigger. Do I need to max out something on his affinity chart first?
There are two requirements to trigger quest - lvl 5 affinity with Dagas (Trust A or better), and corresponding time (sunset, around 4 pm).
It seems you also need Pyra/Mythra in your party.
I couldn't get the quest to spawn either. Then I had one other affinity node to finish (gain affinity in combat 0/15 times).
The quest marker showed up for me as soon as I finished that node. I.e. I completed every other one of the nodes on Dagas' affinity chart besides Cavalier Attitude 5.
I had it unlocked at appears you need to have level 5 affinity, and all nodes of cavalier attitude except the last one unlocked. Then show up at midorl bridge around 4pm to 6pm. Maybe the actual conditions are less demanding.
Though maybe you only need cavalier attitude level 2 for the actual gameplay.