Kunoichi was created by Blackhawks writer Mike Costa.
When Titus escapes the BlackHawks' base, Kunoichi, who is infected with nanocites that goes after him and defeats him. After Wildman and Canada come back from space, Mother talks to her due to the nanocites inside her.
A member of the New 52 Blackhawk team, Nikki Nemzer, there is not much background on the character yet. Kunoichi is a main field operative who became infected with nanocites during an operation and being bit by an enemy pilot. Apparently, against orders, she breached the perimeter during this mission and ended up having to be extracted by a few other members of the Blackhawks' initiative. Though the Blackhawks were supposed to hold clandestine operations, someone was able to capture a picture of both the Blackhawk symbol and Kunoichi upon her extraction. She became "the face of the Blackhawks" and "famous" as a result.
The team, both inactive and active members, recuperated Kunoichi's nanocites get discovered. She was quarantined until further investigation and/or medical analysis could be provided. During this time, Titus (who was captured and unsuccessfully interrogated by the Blackhawks) managed to get free of the Blackhawks containment once the power momentarily shutdown. Kunoichi, coupled with the nanocites' ability to rapidly repair her body, was the only person who could confront Titus once the Eyrie became radioactive and successfully took him down using her nanocite abilities.
Eventually reinstated on the active team, Kunoichi and rest of the Blackhawks became focused on taking down a new threat who had detonated explosives at the Eyrie, killing Wildman. Matteo Bischoff. The entire team, including Andrew Lincoln, moved to take on this threat. Kunoichi, Attila, and Irishman infiltrated the base and Kunoichi was able to confront Bischoff but was almost completely taken out by nanocites that operated like nerve gas. She was saved by Canada but had her body taken over my Mother Machine.
Back at the Blackhawks' base, the Eyrie, Mother Machine attempted to use Kunoichi's body to destroy the base and kill all of the Blackhawks, but was highly unsuccessful. Mother Machine was trapped inside of the base, linked to the mainframe and was blown up as a result of some coolants and things being shutdown, leaving the power sources and nuclear reactor inside to overheat and explode.
All of the Blackhawks escape and are left to figure out what their next move is.
Kunoichi was in a relationship with fellow teammate Wildman until his death. The two have confrontations that lead to Kunoichi avoiding Wildman for weeks at a time until whenever. It was on and off.
While on bed rest she revealed to Irishman that when she was young she wanted to be famous. She also reveals that she even tried out for a Japanese pop-idol group called Team A.