A mysterious beautiful lady that Yayoi encounters.

In the story Yayoi begins to think Satoru has a relationship with her, because she catches them together. But it is soon straightened out when Yukako explains that it was just a misunderstanding and that she already has a fiancee. Both her and her fiancee work at Satoru's father's company as editors. Yukako used to be friends with Satoru's mother but she died when Satoru was only 2 years old.