Mayuko is a young girl who follows Takeshi; she is also a Yaka. Whenever Takeshi finds her, it is at night when she is sleeping in a cardboard box which changes location around the city. Mayuko has a pompous personality and will not hesitate to talk bad of Takeshi around others, but she worries about Takeshi a lot. She became a Yaka many years before the story began when she was killed during a house robbery, and has stayed with Takeshi ever since.