S
Shai Gar is saying that he liked Kira before everyone else started liking the Kira from Death Note, because he (claims he) liked another fictional character named Kira who existed in a fictional universe conceived before the Death Note one was, I reckon.
If this is all true, then yes, "Shai Gar liked Kira before you all did", if none of you also liked that other Kira when it was conceived before Death Note.
So Shai Gar is confessing that he's a Kira Fangirl?