Kodomo no Jikan (TV Series)

This is the story of the surprisingly tangled loves of three elementary school girls. Kokonoe Rin, old beyond her years, is extrovert and energetic, and has a crush on her teacher, Aoki-sensei. Nor is she the slightest bit reticent about showing it, with embarassing explicitness. Her friends, Kuro and Mimi, likewise have love in their hearts, though they are less willing to display it.