Tsubaki is a Diclonius with 30 vectors with a 14 meter range. She is 17 years old, with short, hot pink hair. Four years ago, she was an orphan who lived with a very loving woman. She would tell her stories and teach her how to cook, sew, and sing. Her life changed when the caring woman was injured by another woman who wanted to hurt Tsubaki. Tsubaki, enraged, killed her. She got help for the injured woman and left.
Tsubaki rescues Lucy's dog, ends up meeting Lucy/Nyu 4 years later and lives with her, Kohta and everyone else.
Tsubaki hangs out with Lucy the most. They team up in order to kill Director Kakuzawa, and destroy the equiptment, which brings the end of the Diclonius Research Institute, freeing the others.
Tsubaki is also responsible for the murders of Mayu's mother and stepfather, because she knows about Mayu being abused. Her true goal is to kill all horrible people, so the world would be better. She also knows about rebirthing, as it was another thing the caring woman told her about.
(To Kohta): I'm Tsubaki.
(To Mayu): Yes, I did kill your mom and new dad. I know what they did to you. Any woman who would let that happen to their own child and any sicko who would do that to any kid are not someone we want running around in this world! Those sociopaths deserved it.