It's a chakra disruption basically, it's not a form of genjutsu, just the overwhelming power of chakra through the things Pein uses to send chakra through (As far as my memory can think back to
)
But yeah Jiraiya explains when he gets stabbed by it (When he's in his frog) if I remember correctly
But yeah Jiraiya explains when he gets stabbed by it (When he's in his frog) if I remember correctly