Kaede Fujimiya

Kaede is the twin sister of Momiji and Mr. Kunikida's adopted daughter. Her talents were used to detect Aragami for the TAC, but after realizing she was merely a tool and not a person, she sacrificed herself, only to return on the side of the Aragami. It's not well-shown if Kaede was in love with Kusanagi or not.

Source: Wikipedia