Takeru and Nyaa-tan get along in a bit of a like-hate relationship. Sometimes, Takeru is grateful for the kind things she does but once he figures out her ulterior motive, all of his respect immediately goes down the drain. He finds her a bit less then tolerable and always ends up with an anger vein popping out due to her actions. Despite all this, they are on good terms and care for each other. Takeru also said that without Nyaa-tan it would boring, and Takeru looks after her.
Uri-tan and Nyaa-tan are on friendly terms and care for each other. They are almost seen with each other, and they both treat each other with kindness. Over all, they are on good terms, and probably best friends.
Mo-tan is very attached to Nyaa-tan, (and/or obsessed). Mo-tan said that she always want to cuddle with her, and even loves her. Nyaa-tan however, thinks that this is irritating, and calls Mo-tan a pervert, but despite this, they are on good terms even classing themselves as family.
Considering Dora-tan is Nyaa-tans mentor on the art of Sol/Lull and Mental Strength, both of them are on pretty good terms and have developed a strong bond of friendship. Dora-tan finds Nyaa-tan OK and thinks that she has the most chance of being a Zodiac God.
Nyaa-tan and Ki-tan haven't exactly interacted, but they both are mischievous and enjoy fooling around with each other (together with Inu-tan), and they are on good terms.
Same with Ki-tan, Inu-tan and Nyaa-tan gets along due their personalities and they are also on good terms with each other.
Piyo-tan and Nyaa-tan has a like-hate relationship. They sometimes gets along, but generally Nyaa-tan is teasing Piyo-tan. Due Piyo-tan's bad short memory she doesn't remember why she doesn't like Nyaa-tan but retains the underlying feeling of hatred. Nyaa-tan likes to tease her about this, and Piyo-tan calls Nyaa-tan 'stupid cat'.
Chu-tan has a deep hatred towards Nyaa-tan and wants to destroy the cat clan, due to something that happened in the past. She wants to fight her so she can destroy her. However, in the past, before Nyaa-tan got amnesia, it is revealed that had a close, friendly relationship. This changed when during a battle , Chu-tan got Nyaa-tan's Etotama in her hand using the secret technique Etotama Kagura Senguu and Nyaa-tan's Etotama was injured. That's why Nyaa-tan retained parts of her memories, and ended up with amnesia.
However, After their battle in episode 12, it was discovered Nyaa-tan learned Kagura Senguu first and said that she did it for Chu-tan. Chu-tan also told Nyaa-tan that she felt lonely because Nyaa-tan wasn't there, as she was always traveling. After Nyaa-tan purified Chu-tan's Etotama, she returned to her old self, and Chu-tan is once again friendly towards Nyaa-tan, seeing her as a close friend.