Today, I read a card "Confession" F39 in Kings of the sea. And text is "... Then, discard 1 non-limited card from that hand." I know Limited is a keyword in the core rule,such as western Fielfdoms L59. But I have found a lot of cards indicate "Limit 1 per phase" or "Limit 3 per phase" or "Limit 1 per deck" and so on. So I don't know these cards belong to limited card or non-limited card.

They do not.

"Non-Limited" simply refers to cards without the Limited keyword.

Thanks Ktom. you are really warm-hearted. thanks again.