The Disappearance of Nagato Yuki-chan(2009)

Nagato Yuki-chan no Shoushitsu

This spin-off of the bestselling 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!

(Source: Yen Press)