From JManga:

Junior high student Ken Ishii is good at nothing but getting out of trouble. An unidentified man appears before Ken as he is running away from hoodlums trying to pick a fight, like usual. The man asks "Do you know Zuieki Nogi?" and Ken shakes his head. Two onlookers observe them from a hiding place. The unidentified man unleashes a monster, catching Ken who is unable to get free. On the verge of death, something changes within Ken’s body…!? “Stand up as a ‘Shinobi’leader!” This is his destiny, to be shackled to a dying shinobi family’s fate...