Before the Titanic sank, no one knew it would sink.
Same reason:
No one knows a piranha is a fish until she comes on board.
…
Before Anya met Karl, she had never imagined that there could be such a shameless person in the world!
Same reason:
Before Carl met Anya, he had never imagined that there were such shameless poor people in the world!
…
Supplement: This is a big chase caused by one fish, and this is also a magical drama caused by six fish!
The male protagonist Carl is not ambiguous in 1V1, and does not blackmail the original male and female protagonists.
PS: This article was rewritten because of the previous outline problem. If you guys find that there are similar plots, it's because - the similar article was written by me!