Watch Darker Than Black: Kuro No Keiyakusha: (du...

: In exchange for their gifts, Contractors lose most of their human emotions, making them the perfect, cold-blooded tools for government agencies and criminal syndicates. Meet Hei: The "Black Reaper" Nana Mizuki

: Each Contractor possesses a unique supernatural ability.

That woman is indeed the Nana Mizuki character in this show, yes. Nana Mizuki Kiyomi Asai

Exploring the Shadowy World of Darker than Black: Kuro no Keiyakusha

: Using these powers requires an obeisance —a mandatory, often bizarre task (like folding origami or eating flowers) performed immediately after.