長門有希ちゃんの消失 The Vanishing of Nagato Yuki-chan (Nagato Yuki-chan no Shoushitsu)

Plot

This spin-off of the Haruhi Suzumiya series takes place in the world of the "Disappearance" arc of the original novels, focusing on the high school life (and romance) of a tentative and bashful Yuki Nagato quite unlike the one you've come to know and love through the usual exploits of the SOS Brigade. But no less charming.