It was at the Metropolitan Government Building that Kouki first met Yuki. She was crying, mostly because she had believed that an angel had spirited away Shogo. Although he had no idea what she meant, Kouki agreed to help Yuki in her search. What everyone would find out later was that Shogo was the angel, a result of interference from Apos, and Shogo was using his abilities to get vengeance against those that had used his hacking skills to set-up an international assassination, while at the same time fighting his savage |urges.
After Shogo's death, it appears that Rin gives his Time Fruit to Kouki who, in turn, gives it to Yuki. Twenty years later, Yuki has married Kouki Maeno and they have a son named Teruki. By the time of the events involving Yuki's granddaughter Mishio, Yuki has since died.