Tatsumaki: the Demon wind Assassin is here to protect the weak and use the shadows to strike her enemies down. Like the other Apostles, Tatsumaki has a lot behind her history and what brings her to her current point:

Tatsumaki grew up with her parents in a small village where she spent a lot of her time in the village’s pristine sakura gardens. Her town was raided by the scourge known as the Tengatsu clan, an organization of mercenaries who pillaged and destroyed to further their own money-fueled needs and wants. These assassins destroyed Tatsumaki’s village due to not receiving payment for the services. The leader sensed Tatsumaki had potential as a weapon due to seeing her powers surface slightly during the discord. The leader decided to show Tatsumaki that she would have nothing left, by killing her parents in front of her and burning the village down during their departure. After multiple failed attempts to brainwash and torment Tatsumaki into being a more cooperative weapon, the clan found it best to kill the vampire bat. After taking her to the execution ground, the entire ordeal was interrupted by the Bakurusu, who happened to be wandering the forest at the time. Leaving Tatsumaki to her fate at the claws of the demonic frog, the Tengatsu clan fled the forest and escaped back to their hideout. After barely surviving the encounter with the amphibian and losing an arm in the process, Tatsumaki was saved by an old man who revealed himself to be the true grandmaster of the Tengatsu clan, who was overthrown and nearly killed when he tried to reclaim his position. The elderly man revealed that the clan was initial created to protect and help eliminate threats to various towns and villages, but since his was defeated at the hands of his own disciple, the organization has become a greed and murder driven society that only focused on the interests of the clan and its own goals, willing to destroy and murder countless others in order to further their own ambitions. Revealing everything she lost, the grandmaster felt truly sorry Tatsumaki and apologized claiming that all of this wouldn’t have happened if he had not failed to rectify his mistake. He vowed to teach Tatsumaki the “true” style of fighting and techniques that even the organization did not know, even going so far as to craft an artificial arm for her to emphasize his remorse and willingness to help. Agreeing to stay hidden with the old man and to train alongside him, Tatsumaki felt as if her life was just beginning.

There is more to this story, such as Tatsumaki’s induction into the Apostles, the reclaiming of her arm and even more, but this is just a brief look into her past as to show what she has been through and why she is here to defend the weak and protect the people who matter to her now.
 nim-nim did this pic of Tatsumaki awhile back and I wanted to get some information to you guys so you can enjoy the kunochi bat a little more.

*TRIVIA: Tatsumaki's name literally means "tornado" in Japanese, this is a nod to her ability to manipulate wind and her origin, as her last name Kazeyuki is also a nod to this as "kaze", the first part of her name means "Wind"