Story

Miharu Rokujou has been living a life of indifference for as long as he can remember—which is to say, not that much; he can barely remember his childhood. The life of a normal boy living a normal life planning to own a normal restaurant doesn't offer much, but he'd rather have it that way.

After being pestered by his classmate Aizawa Kouichi and his English teacher Kumohira to join the ninja club time and again, Miharu is attacked by a group of real ninjas... and he still couldn't care less. But when he discovers that the ninjas are after a special hijutsu called the Shinrabanshou sealed within him, and that his new friends Kouichi and Kumohira are actually ninjas themselves, he gets sucked into a conspiracy involving underground clans of ninja and samurai unseen from the public eye, all with their own agendas for the hijutsu. With betrayal and honor at stake, staying apathetic proves challenging, especially when one young ninja from an enemy camp comes forward with a very unusual request.
(tvtropes)