Kekkaishi/Trivia

On Yoshimori's alarm clock just below the pointers it says "Sunrise". This is probably a reference to the Sunrise anime company which hosts anime as well as Kekkaishi.
In episode 41 at about 14:09 when Tokine is telling Yoshimori how to defeat those "black things", she explains how her mother kills roaches. When the roach is shown flying towards her mother, they re-enact the famous bullet-dodge from the Matrix.
In episode 2 when Yoshimori's father and brother are drinking tea and eating cakes, Toshimori is reading the "Shounen Sunday" with "Yellow Tanabe's" picture on the cover.