Teen Exorcist, Vol. 1 (manga)

Japan's Heian Period. Masahiro serves as a royal diviner just like his grandfather, the legendary Abe no Seimei. His dream isn't to follow in his grandfather's footsteps, though--it's to surpass him! During some intense training with his spirit companion, Mokkun, Masahiro notices an ominous presence targeting the princess...Can he protect the royal capital and escape from his grandfather's shadow?!