From Lucia Rose:

A boy returns to his family home in the country and strikes up an odd friendship with the young child who lives next door, Sora-san, who believes he is God. However, it is Plato, the boy's pet turtle, with whom Sora develops a strong bond. Plato believes Sora to be the classical Greek philosopher Socrates and calls her his teacher. Together, they ponder the mysteries and wonders of life in the quiet but beautiful countryside.