Nabari no Ou S01 E01 The Awakened One

"Friend and foe prove difficult to tell apart."

Miharu Rokujou is asked by his classmate, Kouichi, to join the school nindou club. After refusing, Miharu is asked by his English teacher, Kumohira, to join the club. Although the two look like a student and teacher, there's more to Kouichi and Kumohira then meets the eye.