Haruko Nitta is Yūki Mikan's homeroom teacher in her elementary school. She is shown to be an otaku and big fan of Yūki Saibai's work.
Haruko has brown hair and red eyes and wears a pair of glasses.
The most known aspect of Haruko's personality is that she's a huge fan of manga, specifically the work of Saibai Yuuki, who happens to be the father of Mikan Yuuki, whom she considers to be her top student in her class.
Nitta means "fresh, new" (新) (ni) and "field, rice paddy" (田) (ta).
Haruko means "clear weather" (晴) (haru) and "child" (子) (ko).
Haruko made an appearance in Chapter 4 of Mayoi Neko Overrun! when the Stray Cats Association Club were looking for the owner of a lost cat (which was her).