Yasuyo Niwano is a villainess from "Sun Halo" Chapter 34 of Magic Kaito. She was the chief priestess of Nagekomido Temple and Shrine, as well as the owner of thousand years old statue of Goddess Kannon, which is embroided with a golden diamond, whom Kaito Kid targeted.
Yasuyo was introduced in the story by Inspector Ginzo Nakamori to his daughter Aoko and her friend Kaito Kuraba (Kaito Kid's true identity) as the owner of the exhibit of the Kannon Statue, with the villainess claiming that even Kaito Kid himself shall repent of his evil way once he is in front of the statue. However, Kaito identified the statue as a fake due to the differences in pose, items, and accessories, as well as the fact that it a clean cut diamond of this shape was unlikely to exist thousand years ago, and appeared in his phantom thief persona to call off the heist. Unfazed, Yasuyo taunted Kaito for abandoning his target like and old toy, and signaled her cahoots (without Ginzo noticing her) to open a trap door under the exhibit, sending Aoko down along with the fake statue, forced Kaito to drop down as well to save the girl and injured himself in the process due to being stabbed by one of the glass shards from the broken case.
Shortly after Saguru Hakuba arrived to join Ginzo, the evil Yasuyo manipulated the information by claiming that Kaito Kid probably had stolen the remote control of the trap door from the one who had constructed it, Juken Arisato of the Arisato Construction Company. She then made up an excuse to leave the exhibit, informing Ginzo to call for her once the statue has been found. However in truth, the villainess ordered her cahoots, who were later revealed to be employees of the said company, to transport Kaito and Aoko to her temple and throw them inside the secret passage which was constructed into several puzzle rooms, intending to test their wits before she successfully had them fulfill her goal.
Once Kaito and Aoko successfully solved the final puzzle and unlocked the safe, the evil Yasuyo and her cahoots revealed themselves to the two. Yasuyo congratulated Kaito for successfully solving the long unsolved puzzle and had her cahoots restrain the two. The villainess then informed the two of her goal before sending them to hell: she wanted Kaito to unlock the secret safe inside her temple which contained a scroll detailing its construction period and method. With the stated information, the evil Yasuyo planned to get her temple and shrine declared as a National Landmark and to remove insinuation that her temple and shrine were built to mimic the famous Nageireido in Tottori. However, the villainess was outdone by Kaito who had realized her goal and thus swapped his place with Aoko's to steal the scroll inside the safe before her. Having knocked out all of her evil henchmen with his card gun, Kaito proceeded to mock Yasuyo and revealed that the scroll's content is to longer readable due to being keep in such a place for a very long time, which shocked the villainess as her elaborate plan was all for nothing. Nonetheless, the evil Yasuyo claimed that Kaito will still be arrested by Ginzo and Saguru, who had figured out their location and arrived in front of the temple. However, Kaito simply knocked off all the fake wall with his gun, removed the disguises from himself and Aoko, and fled the temple shortly before Ginzo and Saguru entered. The villainess then decided to play innocent and claimed to Ginzo that Kaito had stolen all the priceless treasures inside the safe which she discovered after she returned to her temple. Unfortunately for Yasuso, Kaito had anticipated for this and recorded all her villainous reveal with Aoko's phone, which was found by Aoko and Saguru. With this incriminating evidence, the testimony from her cahoots, and the fake statue, the villainess was then heavily interrogated by Ginzo and the police force and presumably arrested for the crime of kidnapping and attempted murder.