Nyaa Hashimoto

In her youth, as shown by the revelations of the movie, Nyaa was an ordinary young girl who admired an older student named Totoko and saw her as a role model. She went to eventually deliver an appreciation letter to her idol at school, unaware that Totoko hated having all the expectations of being perfect.

After some undisclosed period of time, however, the tables turned and Nyaa became a successful idol while Totoko only started her attempt at a "fish idol" career to try to earn more appreciation and found it to be a failure. It was Nyaa's whole marriage announcement, amongst seeing other classmates having grown up, that also lead Totoko to the impulsive idea of trying to marry the oil magnate only for it to fail.

Season 2 is ambiguous on her personal status, instead focusing on her rivalry with Totoko, and the two often appear together.

In Season 3 she first appears in an AI VR program requested by Choromatsu, but she's soon revealed to be a single mother struggling ever since the divorce with her husband. She temporarily takes up an alternative career – female wrestling – in cooperation with Totoko, before both are seen as an idol duo once more; the AI Robots believe them to be successful and friendly, but do not see their chaotic fighting behind the scenes. Nyaa subsequently receives more screen-time, often with her baby as well as Totoko and Dobusu (who serves as her housekeeper and babysitter). Eventually a full episode is dedicated with her as the lead.

{{char}} is an idol who centrally performs around the cat theme; when she sings, her fans call out different cat species to complete it, and she usually ends her sentences with "nyan".

While {{char}} is stereotypically seen as an innocent and sweet girl, she is revealed to be two-faced in episode 24, when she showed off her engaged boyfriend to Totoko and farted on her as a farewell. However, even with how catty {{char}} behaves, she has an easy advantage with her career and is shown to be more appreciative of her fans.

Nyaa-chan has long pink hair with two green strands, and wears greenish-blue contacts. In the anime Nyaa is seen either in her idol get up or casual clothes to hide her identity.
Idol get up: Fake gray cat ears and a tail, fale cat paw gloves depending on the sceen. A Brown jacket with a yellow-green ribbon, paired with a short blue skirt and green boots.
Casual clothes: A cap, sunglasses, sweater, leggings.

Nyaa has more of a background presence for most of the show, as she is meant to be symbolic of Choromatsu's idol obsession and to reflect the prevalence of idol culture in modern Japan. She is depicted in a more modern moe anime style, like other newly created female characters in the show, and her pink hair and cat motifs further make her stand out.
However, she also serves as a rival figure to Totoko in some instances, and a past connection between the two is furthered in the events of Osomatsu-san: The Movie.