Just gloss over the matter to Lafi.

Quest Text Hey, how many times do I have to tell you that my friend is here?
Do you still have something against us?

Summary No... Why do my worst hunches always come true?!
My grandfather used to tell me how all the daughters of Sylvia were liars!
Regardless, we have a horrible monster spreading a plague!
Does that mean it is no longer safe in there?
Agh, no! Edan is gonna let me have it... He told me to keep an eye on her...
...What? Are you asking about who that person in the forest is?

Summary Shadow Mist Flower...? Ohhhh! R-right!
That's why I was looking for you, but I totally forgot!
The long sealed Forbidden Arena has reopened.
The Shadow Mist Flower is an ominous flower that blooms at the arena.
I've heard rumors of people carrying the flowers, searching for someone.
Specifically, they're looking for those with the Black Spirit NPC Knowledge... like you.
Some of them even went missing.
It's from a credible source, so I'm sure they're not just rumors.
Hey, there's nothing wrong with being careful.
If you ever get that flower, just step on it and burn it right away!