The light-hearted manga is about an adventuring samurai named Kurogane Yaiba who knows how to be a samurai, and little else. Yaiba lives with his father, Kenjurou, in the forest. One day, while Yaiba was eating, a troop of gorillas came to attack. Yaiba and his father escaped and hid inside a box, but they didn't know that the box was full of pineapples and was going to be transported into the city. In the city, Yaiba finds out that he is a legendary warrior and has to fight the evil of a demonic looking high-school student named Takeshi.
The people that Yaiba meets along his journey to become a true samurai encourage him, train him, or inspire him to greatness, though at heart he is still a child, and his incredible skill with a sword is matched only by his kindness towards his friends. Though, he tends to leap before he looks, and his thick-headedness tends to turn potential allies into enemies, though his friends soon clobber him, and salvage the situation. This unlikely group embarks on a host of incredible adventures where they meet legendary figures from Japanese history, and finally overcome impossible odds, and put everything on the line, to save the entire planet from a threat not of this world.
It's a story of love, friendship, hard work, and never giving up.