I'm a fan of ye olde "sworn vengeance upon someone who has no idea what it's about" dealie. It seems very true to real life to me.
I thought I'd made a shading area with Damien at first, but then I realized he's looking through the glass barrier between the room he's in and below. The glass isn't exactly clean and easy to see through at the moment, which I could've conveyed better with fancy brush effects and whatnot, but what's important is that Grace can't see what's going on yet.
Granted, only Nanase and Vlad would be close enough to eye level anyway, but still.