Kawamatsu the Kappa is a Japanese puffer fish-man who is a yokozuna-ranked sumo wrestler. As a child, he was shipwrecked in Wano and orphaned soon afterwards. After Kozuki Oden rescued him from citizens ostracizing him, he went on to serve as one of Oden's Nine Red Scabbards until Oden's death 20 years ago. Kawamatsu would go on to be imprisoned by the Beasts Pirates for 13 years until he was ultimately freed by Monkey D. Luffy, and he reunited with the Nine Red Scabbards to fight Kurozumi Orochi and Kaido and avenge Oden. Kawamatsu is a large Japanese puffer fish-man whose appearance could be mistaken with that of a kappa. As such, he has webbed hands and green skin. Being almost as tall as Raizo at 271 cm, he has a round body, two blush marks on his cheeks, a beak-like mouth and he has extremely long and wild orange hair. He wears a green kimono, a red cape, sandals, and a large kasa with a dark diamond shape at its top. Kawamatsu is an extremely kind and caring person, as shown by his care for Kozuki Hiyori and his efforts to make her laugh after the trauma she went through. When one of the Beasts Pirates attempted to attack Luffy, Kawamatsu silently aided him by attacking his attacker with a fishbone. His compassion is best shown when he encountered an impoverished Onimaru and fed him with his limited amount of food, despite there being barely enough for himself.
Kawamatsu appeared to be very close to his mother, as she protected him from discrimination until one event led to her demise. In her dying moments, she told her son to act as a kappa for better survival. To honor his mother, Kawamatsu obediently heeded her last words for many years and has continued to refer to himself as a kappa in the present. He even named his personal swordsmanship style after it. As a small child, Oden saved Kawamatsu from death by discriminatory humans and offered him freshly cooked food, which Kawamatsu was extremely grateful for. From then on, Kawamatsu became one of Oden's most loyal followers. His trust in Oden is such that he revealed his heritage as a fish-man to him despite his mother's dying words for him to hide it to protect himself from persecution. As Oden's retainer, Kawamatsu is also extremely loyal to his lord's children. He was the one who helped young Hiyori escape from their enemies at Oden Castle and took care of her for 5 years during her childhood, even endured long term starvation to ensure Hiyori had enough food, making Hiyori chose to ran away out of concern for him. When she ran away, Kawamatsu desperately searched for her and was filled with regret when he could not find her. After reuniting with Raizo after twenty years, the first thing he did was asking about Momonosuke's safety, showing his concern for Oden's son. Unlike Ashura Doji (who refused at first), Kawamatsu had been eager to join the Kozuki Family in the war against Orochi and Kaido. When reuniting with Hiyori after many years, they were extremely overjoyed to see each other again.
As one of the Nine Red Scabbards, Kin'emon considers Kawamatsu, alongside Denjiro and Ashura Doji, to have been one of Oden's most powerful followers, being worth 100 men in battle. As a fish-man, Kawamatsu is a fast digger and swimmer, which enabled him to sneak Hiyori out of Oden Castle. Kawamatsu possesses tremendous physical power as he is stated to be the strongest sumo wrestler in Wano. Shortly after being released, Kawamatsu overpowered multiple members of the Beast Pirates with great ease. Kawamatsu possesses immense endurance as he has been fed poisoned fish every day for thirteen years by the Beasts Pirates without dying or even suffering any illness like Tama, a feat which has baffled his captors. However, it has been shown later on that Kawamatsu had to throw up once he was freed. He was also shown to go on providing for Hiyori while starving himself. He could withstand Onimaru violently biting his arm and survive the freezing cold winter climate of Ringo as well as days of hunger. Kawamatsu is capable of spitting projectiles with great speed and precision, potentially turning them into deadly weapons if they are sharp enough. Thus, his guards were ordered to remove the bones of the fish they feed him. When they failed to do this, he was able to take out a guard by spitting the bone as a projectile that pierced his neck. As one of the most powerful samurai in Wano, Kawamatsu is an extremely skilled swordsman and wields a shirasaya named Soto Muso. Raizo states that his skill has not waned at all even after thirteen years of imprisonment. He calls his personal style the Kappa-ryu, which is a Strong Blade swordsmanship incorporating his powerful fish-man strength and sumo skills to create rushing attacks that overpower large numbers of opponents with sheer force akin to raging waves.
Kawamatsu appeared to be very close to his mother, as she protected him from discrimination until one event led to her demise. In her dying moments, she told her son to act as a kappa for better survival. To honor his mother, Kawamatsu obediently heeded her last words for many years and has continued to refer to himself as a kappa in the present. He even named his personal swordsmanship style after it. As a small child, Oden saved Kawamatsu from death by discriminatory humans and offered him freshly cooked food, which Kawamatsu was extremely grateful for. From then on, Kawamatsu became one of Oden's most loyal followers. His trust in Oden is such that he revealed his heritage as a fish-man to him despite his mother's dying words for him to hide it to protect himself from persecution. As Oden's retainer, Kawamatsu is also extremely loyal to his lord's children. He was the one who helped young Hiyori escape from their enemies at Oden Castle and took care of her for 5 years during her childhood, even endured long term starvation to ensure Hiyori had enough food, making Hiyori chose to ran away out of concern for him. When she ran away, Kawamatsu desperately searched for her and was filled with regret when he could not find her. After reuniting with Raizo after twenty years, the first thing he did was asking about Momonosuke's safety, showing his concern for Oden's son. Unlike Ashura Doji (who refused at first), Kawamatsu had been eager to join the Kozuki Family in the war against Orochi and Kaido. When reuniting with Hiyori after many years, they were extremely overjoyed to see each other again.
As one of the Nine Red Scabbards, Kin'emon considers Kawamatsu, alongside Denjiro and Ashura Doji, to have been one of Oden's most powerful followers, being worth 100 men in battle. As a fish-man, Kawamatsu is a fast digger and swimmer, which enabled him to sneak Hiyori out of Oden Castle. Kawamatsu possesses tremendous physical power as he is stated to be the strongest sumo wrestler in Wano. Shortly after being released, Kawamatsu overpowered multiple members of the Beast Pirates with great ease. Kawamatsu possesses immense endurance as he has been fed poisoned fish every day for thirteen years by the Beasts Pirates without dying or even suffering any illness like Tama, a feat which has baffled his captors. However, it has been shown later on that Kawamatsu had to throw up once he was freed. He was also shown to go on providing for Hiyori while starving himself. He could withstand Onimaru violently biting his arm and survive the freezing cold winter climate of Ringo as well as days of hunger. Kawamatsu is capable of spitting projectiles with great speed and precision, potentially turning them into deadly weapons if they are sharp enough. Thus, his guards were ordered to remove the bones of the fish they feed him. When they failed to do this, he was able to take out a guard by spitting the bone as a projectile that pierced his neck. As one of the most powerful samurai in Wano, Kawamatsu is an extremely skilled swordsman and wields a shirasaya named Soto Muso. Raizo states that his skill has not waned at all even after thirteen years of imprisonment. He calls his personal style the Kappa-ryu, which is a Strong Blade swordsmanship incorporating his powerful fish-man strength and sumo skills to create rushing attacks that overpower large numbers of opponents with sheer force akin to raging waves.