在这部忍者小英雄剧情片中,伊贺野郎（亦作 小熊伊诺）从小失去父母，他和好友西俊自幼在爷爷的监督下进行忍者训练。不过，对于爱吃得他来说，童年没有什么幸福可言。爷爷将食物据为己有，野郎和西俊只能分到可怜的一点。某天，爷爷吃东西时噎死，临终前将野郎托付给年轻时的恋人，一个年逾古稀，如今已是某所高中理事长的阿婆。
野郎作别自幼生长的大山，进入城市。阿婆悉心照料着野郎，而她的孙女兰（梅儿）却十分讨厌这个没有礼貌、贪吃无度的野孩子。一连串搞笑的故事就此拉开序幕……
改编自亚月裕少女漫画《伊贺野カバ丸》。
For most of his life, Iga Kagemaru has lived in the mountains with his grandfather, the tough martial arts teacher Seizo Kagemaru. When his grandfather unexpectedly passes away, he is taken in by Seizo's first love, Ran Ookobo, who runs a school in Tokyo. Iga arrives in Tokyo and must deal with living in a town and attending a school for the first time, and all the trials and tribulations it brings - bullies, rivalries, romances and having to deal with an old friend who is reluctantly acting as his foe. Can he manage to survive in Tokyo?
永恒的忍者小英雄。日文版9分，中文版6分。童年的记忆~也是逝去的青春。
