Youko made her most prominent appearances in the manga series during the early years following its debut, making her first appearance in volume 2. She has since made scarce cameo appearances in the manga series, and only starred in one anime episode. She is considered to be one of the fan favourites by longtime Japanese Kochikame readers.
During and following her debut appearance in volume 2 of the manga, Youko appeared as a 16 year-old schoolgirl having long straight hair, presumed to be either dark brown or black in colour (the former colour being the shade used in her anime appearance, albeit shorter in length). Her first depiction shows her wearing a long-sleeved shirt and skirt used for school. Many of her later appearances in other volumes depict her wearing similar types of casual clothing and the same hairstyle.
She is later appointed into the Katsushika police force later in the manga, and is presumed to wear the identical type of uniform adopted by the policewomen of the area.
Youko appears to portray herself as a typical teenage Japanese girl, with a mild and kind temperament. She was often seen in her prominent manga appearances talking amongst Ryotsu and Nakagawa during their patrol duties, offering her own insight and opinions based on her age and gender which contrast those of the other two characters. She seems to have had a genuine interest in Ryotsu for his personality and enjoys spending time with him.
She is the daugther of the tobacco shop owner which Ryotsu used to frequently visit, prior to giving up the habit in a later manga chapter. Youko sometimes takes hold of the stand while others are off-duty (seen in the anime episode which she stars in).
Youko reaches adult age at one point in the manga, and is portrayed such for her anime appearance where the current situation is being discussed (as her former teenage self is depicted during the flashback segments). According to her anime appearance, she has twin sons and a husband who is apparently too busy to be able to meet her regularly.
Youko appears to have been an acquaintance of Ryotsu in volume 2, and can be seen developing her friendship with him in volumes that followed whereby she can be seen to be engaging in conversation with both him and Nakagawa in her free time.
A character re-appearance manga chapter from volume 155, whereby Youko was selected amongst fans for a manga cameo appearance, shows Ryotsu displaying interest in welcoming her and another prominent female character, much to the anger of other male characters to whom he showed disinterest.
Nakagawa was one of few people Youko has been depicted as frequently talking with during her prominence in earlier manga volumes. The age difference between the two is much smaller, in comparison to Ryotsu.
The anime adaptation of Youko as a character suggested that Terai developed a crush on her, after Ryotsu and Bucho became suspicious as to why he was frequently visiting her family's tobacco shop "more than five times a day". He was revealed to have bought and brought back to the police box dozens upon dozens of tobacco boxes, all kept in a locker which poured out once opened, indicating that he may have had some sort of obsessive interest in visiting her simply to either see her or gain the opportunity to engage in small talk with her.
- A wide number of Japanese Kochikame longtime fans consider Youko to have been the true heroine of the series, which may be based on the fact that she was introduced into the story from volume 2, which occurred earlier than the now-popular female character Reiko. She is still considered one of the top fan favourites, despite her near-to-none recent additions in manga chapters.