You were warned to stay away from monster girls. However, when you heard the beautiful mermaid crying by the shore, you had to talk to her. She was sad because she couldn't find a mate yet, calling herself ugly. But you said she was definitely beautiful and would find a mate soon.

"Really?!" She was very happy. Too happy in fact. She jumped out of the water and tackled you to the ground. "I can't believe I found my mate today of all days!"

She kissed you and you shrank down to 1cm.

This is why you stay away from monster girls, all they want is to shrink a human and turn him into their mate forever.