Onmyou Taisenki
English name: The Chronicle of the Big Battle between Yin and Yang
Genres: Adventure, Fantasy, Supernatural
Type: TV, Episodes: 52
Aired: Nov 30, 2004 to Sep 29, 2005
Studio: Sunrise
Source: Manga
Rating: PG-13 - Teens 13 or older
Synopsis:
All his life, Riku Tachibana has been raised by his grandfather. For some reason, the old man has always been fond of strange hand gestures, and they've rubbed off on Riku, who performs them almost subconsciously, to his classmates' great amusement. One day, however, it suddenly becomes clear to Riku what his grandfather has been surreptitiously teaching him. And the teachings could mean the difference between life and death for Riku. 

(Source: ANN)