Kekkaishi.

"By night, junior high student Yoshimori Sumimura is a "kekkaishi"--a demon-hunter who specializes in creating magical barriers around this prey. By day, Yoshimori's got other demons to battle: an addiction to sweets and a seriously crotchety grandfather! Yoshimori's pretty 16-year-old neighbor and childhood friend, Tokine Yukimura, is also a kekkaishi, but their families are feuding over who is the 'true practitioner' of the art.