Stats are a way you can increase your fighting prowess in Grand Piece Online. They are divided in several categories and can be accessed through the menu.
Everytime you level up you gain 3 stat points, which can be distributed into any stat to increase its effectiveness. Your health and stamina will also raise by 1 passively.
Strength - Strength raises the damage output of physical damage, such as skills from fighting styles, such as Black Leg or Rokushiki, up to a certain limit. This stat does not affect damage inflicted by swords, guns or Devil Fruits.
Stamina - Stamina increases a player's stamina, giving 2 more stamina per stat point allocated. Stamina is used by most of the moves in the game, such as attacks done by Devil Fruits. This stat does not affect stamina regeneration.
Defense - Defense increases health, health regeneration and block strength. Each point in defense adds 2 health and 1 more hitpoint to your shield. Defense also increases the damage output of the "Self Destruction" skill of Bomu Bomu no Mi.
Sword Mastery - Sword Mastery unlocks sword skills and increases the damage done by all weapons categorized as swords, examples being the Katana, the Golden Staff, Elo's hammer, Flower Bouquet, and many more. Sword Mastery also increases the damage done by the Tori Tori no Mi ability Phoenix Talons.
Fighting Style Mastery - Every melee fighting style has its own unique mastery stat required to unlock skills. This stat does not increases the damage of fighting styles. Exceptions to this are Electro and Fishman Karate, whose skills increase in damage by mastery, while strength affects M1 damage.