Trying means a lot. Giving Seifer a chance means a lot more than he can ever articulate. The fact that she's trying to accept this, no matter how questionable, does mean something to him. While he can't quite grasp the full severity of her concern over Darkness, he does understand he's probably flirting with trouble here. The question there is when isn't he? He doesn't know, but damn if he did know he'd be really touched.

"You'll be one of the first to know," He promises. Easy enough to keep, she's his roommate and all. He nods slowly at her confession, frowning slightly. "What's it do, how d'you know it's becoming a problem?"

Seifer could use a big sister or two to keep him in line. He makes bad life decisions a hobby.