Noroko is one of the main characters from the The Black Heart. She is a ghost who lies dormant within an ancient Japanese doll which is currently owned by an antique collector. She is heavily based on Japanese horror films and folklore, taking inspiration from the Onryo ghosts: typically female spirits who suffered violent deaths that now seek vengeance upon the living.
When the king of the other world is murdered and his heart is ripped out, the power emanating from it was strong enough to awaken Noroko who escapes the doll and kills the collector. Noroko travels through the worlds searching for the heart currently in possession by Final hoping its power can end her suffering and grudge, which is so powerful it drives her to attack and kill anyone she comes across.
In M.U.G.E.N, Noroko has been made by Andrés Borghi. While Noroko was initially exclusive to The Black Heart, she was released for regular M.U.G.E.N some time after the game's initial release.
Andrés Borghi's version
Noroko is a four button character ((Z) and (C) don't do anything besides work as "shortcuts" for her super moves) with high mobility and very powerful air combo potential. The relative short range of her command kicks and punches however force her to stay really up-close to her opponent if she is to deal high amounts of damage. This makes her vulnerable to fighters who can zone her out with projectiles and long range physical moves like Dhalsim.
With good prediction, her ability to teleport when cornered and access to a counter move gives her an edge against rushdown tactics. While short ranged, she can also do rushdown, using her special moves she can close gaps quickly and then extend her air combo to ridiculous lengths while pinning enemies against a wall.
In Killer mode, she will turn from an agile short-range fighter into a slow and small but powerful projectile spammer. While in Killer mode, she relies on creating a gap between her and her opponent to unleash great amount of projectile attacks. She is completely unable to jump or block attacks while in this mode and can be punished harshly if she is caught out of position, she cannot be combo'd but the ease in which one can stun her with basic attacks makes this advantage null. Like all killer modes, she performs a special super attack if she transforms in the middle of a combo.