Hotori: Tada Saiwai wo Koinegau

A young boy named Ryo perished in an accident long ago, and at his parents’ wishes he lives on through an android named Suzu. He must regularly have Ryu’s memories artificially injected into him, and undergo a series of tests at the personality plant he resides at. During a session testing his motor movements, Suzu loses a baseball inside another building and goes exploring; there, he meets a young girl of the same age named Hotori. Though Suzu is an android, he still is able to present human emotions, and feels disheartened when he learns that Hotori rarely leaves the room. More importantly, Hotori suffers from a disease in which her memory rapidly deteriorates. Suzu and Hotori soon form an intimate bond, and question what it really means to live. (Source: Anime Planet)