After the death of Saizou, Kabamaru's horribly strict grandfather and iga ninja-sensei (teacher), an old lady Ran Akoko claims that she received a letter from him asking her to take care of his grandson. So Kabamaru runs off with Lady Akoko to the big city Tokyo to gorge himself on yakisoba, Ramen, chow-mein and attend a regular school which turns out to have weird quirks of its own.

As an electronic war erupts in the last decade of the 21st century, mankind returns to their pre-historic primitiveness and the ages-old jealousy-inspired conflict between brother and brother over a woman erupts again.