@Karinkishi
well, it depends on how her future vision actually works...
It's possible she only sees a vision of what could happen if nothing is done.
and also at the end of the day, you can always blame the butterfly effect.
Mabey because the girl told her dad, who went looking for the random dude who got gifted the armour.
the lack of the random guy's presence ( because he got hired ) somewhere down the line could have indirectly caused the MC to be at the wrong spot when the demon attacked.
Now because the random dude wasn't there to fuck up the MC´s day, he could save the day without knowing the demon was even there instead of going off on some random hunt?
is it longwinded? heck yes, but that's life when you have a future vision in these types of stories.
Sometimes the future vision itself is the cause of the disaster that is predicted in the vision of the future, and everything would have ben fine if they different try to predict the future in the first place.