Based on what had been said, i doubt the NTR dude cursed her or something.
Most likely, the NTR dude wants the girl because there is chance of someone suffering from the Mana Overload Disease to gain a powerful or unique Job upon being cured.
Its might be possible that the longer one had the disease and the longer they survived, the better chance of getting a rare Job.
This is probably what that NTR guy's target is, aka., he wants to get her because of her potential.
Maybe, he wants to create a strong party with strong/rare job holders, or is looking for someone with a specific job, or has ability to take the Jobs of other people.
There maybe various possibilities.