He drops the third feather into the water and watches it gently float toward its fellows. Another follows soon after and another and another. When his pouch is empty, he takes a step back and watches the lake slowly settle back into its untouched state despite the feathers.
There's a part of him (the part that's left from when he believed in Shinra, from before the plate fell) that prays this will make a difference. That enough Phoenix Downs will fix it.
But they can't and they don't. The feathers keep drifting, drifting and the only thing breathing here is him.
Thoughtfully, he fingers the materia in his pocket—to say Yuffie was the only materia thief would be a lie, but he intends to return it, soon—and calls Phoenix. The great fire bird appears, and flaps around the lake for a time, stirring the water and the feathers, and then it gives a great caw and disappears.
It's not much of a surprise, not really. Death isn't something that can be solved by items or materia or anything else.
Reeve passes a hand over his face, and blinks back tears for a woman he never had the opportunity to meet.