The Princess Reincarnation summary:

"It is said that a mermaid's tears will become a mysterious jewel."Aisha, a girl who never sheds tears despite being bullied. The day she ran away from the village, she became a mermaid.Grand Duke Hayden Elikin visited."We are family, Aisha Elikin."Overnight, her life gradually changed. Hayden took good care of Aisha and told her that she was his old sister, but that was clearly a lieAisha, who has learned the way of life of a mermaid and a dazzling princess. Will she be able to stay with him despite knowing Hayden's secret? Tears of the jewel is Aisha or Hayden?