Hotori ~Simply Wishing For Hope~

At the Personality Plant, robots are being built and slowly outfitted with the artificial memories of real people. Suzu is one such robot, being made to replace the young boy a family has lost. By chance, he meets a Hotori, a young girl suffering from progressive memory loss. The two children become friends and attempt to define themselves in the light of their changing memories.

(Source: Anime News Network)