You can meet Nyoko ingame in HKO on the harbour of Sanrio Harbour, either standing around next to the lighthouse or lying in the sun looking quite different in time of events like Valentine's. Nyoko/Nyako loves hamburgers - this will always stay the same! Nyako is one of Usahana's close friends, like Puppi, Panya and Sora. You can read more about them on this - japanese - website, if you can read Japanese, that is: [1]
The pirate's guild (thank you very much! http://www.hkopirateguild.com/ ) have found out more about Nyokos second image that you might find on Valentine's or at other event days ingame in HKO. "Nyokos" real name in this "form" should be "Nyago" or "Nemukko Nyago" (Japanese tabby cat), her birthday would be on May 25 (2000), and she would live in a town in Japan. Nyagos hobby is sleeping and she is looking for friends to take naps with.