Memoru is one of 245 people who came to earth from the Riruru Star when their ship had an emergency crash-landing on earth. Memoru's people have such tiny bodies that they could stand on a human's palm. One day she hears lovely music, and she follows its source and comes upon a huge house she hasn't seen before to find a girl taller than her playing on the piano. Memoru visited her again secretly with her friends Popitu, Rupangu, and Pi, but the human girl, Marielle, seemed sick and likely to die any moment. Feeling sad for the girl, Memoru's tear drops on the girl's lips. The girl gets better and a strong friendship starts between them.
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(Source: Anime News Network)

Marielle is a young girl currently living in a remote house deep in the mountains between Switzerland and France to recover her health. The story is told through the memories of her adventures with Memoru, a tiny alien girl who lives on a nearby island. Her people are gnome-like beings who are stuck on Earth after their spaceship crashed here.