Nyaruko (ニャル子?) is the main protagonist of the anime, manga, and light novel series and the main heroine of the visual novel game. Nyaruko is a race of alien known as a Nyarlathotep which was originally featured in Lovecraft's books as a type of monster.
In order to blend in, she takes the name Nyaruko Yasaka as Mahiro's cousin even staying at Mahiro's house. She even begins to attend to his school to get closer to him despite the fact she has already graduated before.
She mainly uses her own form of Space CQC close-quarter combat weapons while fighting, with her weapon of choice being "Some Kind of Unspeakable Bar Thing". While in full force mode she adorns a black and red helmet with armor that covers her entire body.
She takes the form of a human girl with long silver-colored hair, but jokingly says to Mahiro that she can change to her original form if he wants her to.
Nyaruko has long, silver-colored hair and bright green eyes.
Her most distinctive feature is a long strand of hair on top of her head, changing shape whenever she feels a strong emotion. For instance, when she thinks about her romantic relationship with Mahiro, her strand of hair often curls into a heart shape. Her hair may sometimes take other shapes, such as changing into a zig-zag shape whenever she gets angry or jealous.
She is always friendly to Mahiro, eager to pursue him, but often shows abusive and brutal habits to any hostile aliens.
She claims to be one of the best fighters on Earth, as she states that her combat level is 530,000, while a normal farmer armed with a hunting rifle is 5 (though this may be a parody of Dragonball Z). Despite this, she is always unsuccessful when dodging Mahiro's fork attacks.
She happens to be smart and self-confident, as she graduated from one of the best universities at the top of her class. She has even shown fourth wall awareness and hints seemingly towards the viewer(you).
Her actual age is unknown since she always stops Mahiro whenever he becomes curious or questions her age.
Nyaruko is shown to be highly into gaming, and says that Earth's entertainment is well known to aliens across the universe. She is also obsessed with otaku culture.
Her feelings towards Mahiro are serious, with her going so far as eventually talking about marriage and a family together.
It has been shown that Nyaruko can easily irritate Mahiro with her actions, words, and especially regarding her love for him.
Ever since Nyaruko confessed to Mahiro that she was in love with him, her presence around him can sometimes fluster him. As time goes by, the two of them spent more time with each other. Mahiro began to grow attracted to Nyaruko as a woman.
Nyaruko and Kuuko have known each other for quite some time and even went to school together.
Generally, she has trouble dealing with Kuuko, who loves and desires her, despite the many reasons that might hold them apart.
- Her birthday is on April 15, 2009 (the day the first light novel was released).