- "Kachikachi" is the Japanese onomatopoeia for stones knocking against one another to create fire, a reference to the heating up power of the fruit.
- "Kachikachi" can be the sound effect of something hardening, another reference to the powers of the fruit.
- The FUNimation sub names this fruit as the Hard-Hard Fruit.
Strengths and Weaknesses
This fruit allows the eater to harden the body at will, increasing defense capabilities. Not even the drilling power of the King Cannon could break through it, as it was the floor caving in that defeated him. The user can also increase the temperature of their hardened body portions, which can be used to increase damage done to the opponent, enough to set his chair ablaze upon contact.
This fruit does not seem to have any other specific weaknesses, aside from the standard Devil Fruit weakness.
Bear King basically hardens his body to increase defense. This also augments his offense, allowing him to hit harder. He also increases his body temperature to burn his opponent on contact.
- Hot Boiling Special (ホットボーリングスペシャル Hotto Boiringu Supesharu?): Bear King heats his fist up and punches the enemy.
- The "heat-up" ability appears 3 times again in the anime, from the Atsu Atsu no Mi, eaten by Don Accino, the Gutsu Gutsu no Mi eaten by Bill, and the Netsu Netsu no Mi eaten by Oven.
- The power to "harden" the body for both defensive and offensive enhancements is also reminiscent of Busoshoku Haki and the Kira Kira no Mi.
- One Piece Movie — Clockwork Island Adventure, Bear King is revealed to have eaten the Kachi Kachi no Mi.
- Kachi-kachi Yama – Wikipedia article about the Japanese folktale the "Kachi Kachi" sound is often referred to.
- Netnihon Fairy Tales & Legends: Kachi-kachi Yama - Netnihon Fairy Tales and Legends entry about the Japanese folktale the "Kachi Kachi" sound is often referred to.
- Kachikachi-yama - Kids Web Japan folktale entry about the Japanese folktale the "Kachi Kachi" sound is often referred to.