Iga No Kabamaru

The eponymous protagonist is a naive young ninja from the Iga province called Kagemaro (absolute shadow), nicknamed Kabamaru (hippo's mouth) for his insatiable appetite. After the death of his strict grandfather and ninja sensei, Kabamaru moves to Tokyo with one of his grandfather’s acquaintances. The plot deals mainly with Kabamaru adjusting to an urban lifestyle after spending a childhood in the mountains and how he finds himself caught up in the rivalry between two private schools. (Source: Wikipedia)