Kiko begins as the 12-13 year-old cousin of Tomoko and Tomoki Kuroki. She first appears in the manga Chapter 14 and in the anime Episode 8 to visit the Kuroki family. Her mother appears "off screen" in the manga. While she is first amazed with Tomoko's stories about having a boyfriend, when she finds out Tomoko has been lying to her all this time, she starts to act superior to her. Eventually, Tomoko suspects that Kii treats her like a pet dog.
It is implied that she is cheerful, since she is usually smiling. However, she is not as gullible as she once was before going into middle school, and Tomoko soon catches wind of this.
(Source: WataMote Wikia)