Purrloin is Azusa fifth Pokemon she caught prior which was briefly mentioned, and she also appeared in a flashback, where her Purrloin lives at her home as a house cat. She is also Azusa's first Dark-type, she was given the nickname "Azu-nyan 3" by Azusa Nakano herself.
In one episode, she began to show signs of evolving, but resisted the glow and stopped herself from evolving much to Azusa's confusion, she later explains to her that she is happier as she is as a Purrloin, and evolving into a Liepard would make her look scary for Azusa, Azusa herself was on the verge of tears hearing Azu-nyan's story that Azusa decides not to evolve her, much to Azu-nyan 3's delight. As a result, Azusa gave her an Everstone charm on her neck so she'll stay Purrloin forever.
It was later shown in Purrloin's backstory that she was just an Egg when Azusa found her as an egg, she looked after it nonstop and it finally hatches the next morning, as a baby, she was very playful an affectionate and sees Azusa as her mother.
Azu-nyan 3's known moves are: Play Rough, Iron Tail, Night Slash, Hidden Power, and her ability is Limber.