Name- Hamato Yang Neko Mao Yin

Nicknames- Mao Yin, Hyinmy, Neko,Yinny, Kitty, Kitty Cat, Greenie, Sunspots, Freckles,(Copper/Brown by Casey)

Age- 16 1/2

Personality- Mao Yin is a loyal fun loving girl who takes her responsibilities heavily, she is clever and fun loving and encredibly creative, Some of her favorite activities are metalworking/weapon making , Training with the boys, and trying all sorts of crazy stunts in order to find her fighting style

Weapon- Kyoketse Shoge

Background- She was an orphaned infant/toddler when a mysterious sequence of events caused her basket to fall into the sewers, Master Splinter adopted her in hopes he could give her the life Mi Wa never had, She was raised along side the boys and learned quick, she became a skilled fighter and even though she was on the same level as her brothers Master Splinter always seemed to shelter her much more than the boys. Her first mission she had to sneak out with the boys to be able to go on it and afterwards Splinter realised her potential and "loosened her leash". She was the first to meet Karai and at first they considered themselves mortal enimies, when shredder heard of Splinters second daughter he imediately kidnapped her to rub more salt in the wound. She was treated at the mercy of Karai leading to brutal beat downs and other forms of vengance. The turning point was when Karai tried to strangle her with a metal baton by forcing it against her throat while she was backed up to a wall. Just as Mao Yins face started turning purple she smiled at Karai and told her You have such beautiful and familiar eyes.... Karai pulled away bewildered at the way she was able to go through torture without a tear.... It scared her.
The boys soon freed their sister and she asked Splinter about Karai to no avail. Their next interaction came from after she had been kidnapped again and forced to poision herself so that shredder would spare the lives of her brothers. She complied but was found before she was killed by a very determined Donnatello. For a month she was in a coma in Donnies lab living off of a machine the braking point was when her heart stopped suddenly and Donnie brought her to a human hospital. Karai heard of Mao Yins state and her guilt started to slowly develop. A week later she awoke from the coma and was moved to a mental facility after claiming to be raised by a Ninja Rat and Turtles, It was there she met Morganite Willace the Daughter of a wealthy buisness owner who had left her there since she was 8, She was constantly escaping and the two girls friendship grew rapidly. After a fight between staff and patients in which Mao Yin used ninjutsu to try and escape from the facility, she was taken down using Five times the sedative a normal girl her size would have required. She was moved to solitary confinement strapped down to a table with a sheet over her face at almost all times, after a week of this treatment donnie finally found her new location and came with the team to break her out. She refused to leave without her new friend that mikey imediately realized as Ignite the Vigalante/AntiHeroine. They brought her to the base at Mao Yins request and she eventually joined the team. During a fight with shredder Mao Yin was exposed to a few drops of mutagen and turned into her first mutant form an anthropomorfic spider that Mikey fittingly named Spindles. After a few hours she demutated and started a line of Donnies new experiments, trying to find why she alway reverted. He discovered that her cells had strange properties of both mutagen and anitmutagen, They were in a constantly changing state even when in her normal human form. However her body and mind suffered damage everytime she mutated and started to get sick, each of her mutated forms haunted her mind and constantly tried to gain control and resurface. It seemed as she would soon die as she kept getting worse and worse until during a fight Donnie tried to block her from a splash of mutagen but instead mutated with her creating a strange fusion of the two while their minds stayed in tact. After a few hours they un fused and returned to their normal selves with an exception Mao Yin was seemingly healed.
The time she stays mutated depends upon the amount of mutagen she is exposed to.
More of her story will be added later but I think that is enough comic spoilers for now XD!