Mahou no Mako-chan
Genres: Fantasy, Romance
Type: TV, Episodes: 48
Aired: Nov 2, 1970 to Sep 27, 1971
Studio: Toei Animation
Source: Unknown
Rating: G - All Ages
Synopsis:
Mako is a young siren and daughter to the King of the Sea. In a stormy day she rescues the young sport Akira from a wrecked ship, but ends up falling in love with him. So, with help from the Witch of the Sea, she's transformed into a human, and becomes a highschool student who helps everyone with her strong sense of love and justice and her magical pendant, the "Tear of the Mermaid."

(Source: ANN)