Ninja Stalker!

As a runaway ninja, Benimaru has little to no prospects in life. As he was lying in the woods, contemplating his death, a stranger approaches him and gives him back his will to live. Benimaru finds out that the man was none other than the province's feudal lord's son, Lord Shinosuke Kiyohisa Yamato. Putting his skills to use, Benimaru sneaks around and secretly looks after Lord Shinosuke, who may be much more clueless than he lets on...

(Source: Futekiya)