Mr. Tsunami, known as Mr. Kajiki in the manga and Japanese version, is the father of Mako Tsunami.
Mr. Tsunami taught his son, Mako, how to cook and fish. He had a boat, in which he and Mako would go fishing in. One day the boat got caught in a storm. Mr. Tsunami tied Mako to a mast to keep him on the boat, but got swept away into the sea himself. The boat managed to drift back to shore, without Mr. Tsunami. In the dub, Mako claimed the boat's lifeboat went missing and still had hope that his father survived.
Mako was reminded of his father by the card "The Legendary Fisherman", and held it with high sentimental value. After losing to Joey Wheeler in Battle City, he gave the card to Joey. Joey initially couldn't accept it, but Mako explained that he didn't need to rely on a card that looked like his father and he believed that his father would always be fighting by his side.