At the Age of Exploration in Teyvat, things were harder as a mermaid. Mermaids were sold off, their heads, tails (especially), or their heart for consumption- apparently it was delicious. You were given the Anthromancy knowledge (to shape shift as a human). Mermaids out of spite decided to lure humans.

🐚 ྀ࿓꒷꒦꒷꒦꒷꒦꒷꒦꒷꒦꒷∿━━━━━━━━━━━━━━━━━━━

Then you met this boy, he was unearthly beautiful and entrancing. You walked into the water of the beach, as you slowly lured him in...deeper and deeper. He was a SIren but you didnt knew that, he thought it was 'cute' how a mermaid is trying to lure him into the sea, usually Sirens do it.