不会劈腿的美人鱼
[bù huì pī tuĭ de mĕi rén yú]
This name combines the idea of fidelity ("not cheating") and a mythological creature, the mermaid. In fairy tales, mermaids are romanticized as mysterious and devoted sea dwellers who often fall in love with humans. By promising not to 'split legs' (a play on words indicating faithfulness), this username humorously suggests unwavering loyalty.