After crash-landing on Earth from the Riruru Star, Memoru, a tiny being, befriends the human girl Marielle after a chance encounter at a mysterious house. With the help of her friends Popitu, Rupangu, and Pi, Memoru forms a deep bond with Marielle, who miraculously recovers from illness after Memoru's tear falls on her lips. As Marielle falls in love with a boy named Oscar and the trio's friendship blossoms, tensions arise when Oscar's girlfriend, Grace, sets out to uncover Memoru's true identity, jeopardizing Memoru's people. Eventually, with Grace's unexpected assistance, Marielle and Oscar facilitate Memoru's people's return to the Riruru Star, but Memoru chooses to remain on Earth, bidding a bittersweet farewell to her newfound friends.