This mini quest can be found at the train station you gain access to once you’ve completed the Train Graveyard dungeon. You’ll see a woman standing near the steps. Talk to her and she will tell you about her problem and that she needs inspiration. She asks you for a lady mirage.
You don’t have to actually give her a mirage, but you must have a female mirage in your party somewhere when you return to her. She will thank you and you’ll get an Accuracy+ Seed.