Slang term derived from ナルシシスト (narcissist), often used playfully or critically to describe someone who is self-absorbed or vain.
See also: ナルシスト
He always talks about himself; he's such a narcissist.
SNSに自撮りばかり載せるナルちゃんは多い。
There are many narcissists who post nothing but selfies on social media.