Asatte no Hōkō (あさっての方向。, Asatte no Hōkō? lit. A Direction of the Day After Tomorrow) is a Japanese series about a young girl who grows older into an adult, and an adult woman who becomes younger, turning into a child. It first began as a manga series authored by J-ta Yamada, which started serialization in the Japanese manga magazine Comic Blade Masamune on March 3, 2005. Since then, the series has been adapted into an anime series which began airing in Japan on October 5, 2006, produced by J.C.Staff.

Source: Wikipedia