From the One Piece card game official website, the basic knowledge of the cards in the battles have been revealed in Japanese.
There is 5 different types of cards in One Piece Card Game. They are Leader Card, Character Card, Event Card, Stage Card and Don Card.
Condition to win the game:
(1) When the Leader's life is at 0, a final attack will win the game.
(2) There is no more cards in the deck (Deck-out)
Deck Structure:
The One Piece card game deck includes:
- 1 Leader card.
- A deck with 50 cards of the color of your leader that contains character cards, event cards and stage cards (you can only play up to 4 cards that has same code number)
- 10-cards in Don's deck.
Starting the game:
- Shuffle your deck and Don!! deck and put them in their respective zone
- Place the leader card in its zone
- Decide the first and second player with rock-paper-scissors.
- Draw 5 cards from the top of your deck.
- Only once, you can return all your hands to the deck and shuffle them (mulligan), then you can re-draw five cards from the top of your deck
- From the top of your deck, according to the life of your leader, place cards face-down in your life zone.
- The first player starts their turn.
Game Flow
Refresh Phase:
- Return to the cost area all Don!! cards attached to cards in your field.
- Untap all the rested cards to active state in your field.
Draw Phase:
- Draw 1 card from the top of your deck (The player who goes first does not draw in their first turn).
Don Phase:
- Reveal the top 2 cards in your Don deck and put them in cost area (The player who goes first only reveal and move 1 card in their first turn).
Main Phase:
You can do below 4 bullets in any order
- Bullet 1 – Playing cards: based on your card cost, rest Don!! cards in the cost area for the cost of the card to play that card. (Event cards is moved to the trash after playing).
- Bullet 2 – Attaching Don!! cards: Attach active Don!! cards to your leader or characters in play (If the cards leave the field, return Don!! cards to cost area in rested state).
- Bullet 3 – Activate effect of the cards: Activate the effect by fulfilling the conditions of your leader and characters.
- Don!! x1: This card need 1 Don!! card attached to it to activate its effects.
- Don!! -1: Return 1 of your Don!! card to the Don!! deck to activate the effect.
- Active Main (1): Activate by resting 1 Don!! in your cost area.
- Bullet 4 – Attacking: You can use your leader or character cards to attack your opponent, trigger the attack by resting them.
- Card cannot attack the turn they are played (except "Rush") and neither player can attack on their first turn.
End Phase:
Effect that lasts "until the end of this turn" are negated, and your opponent's turn starts.
Translated from the Rulebook, Credit to Woddish (Discord account)
Setting up the board:
1. Both players must place their deck in the Deck Area before revealing their Leader.
2. Life cards can be placed and taken in any order.
General Gameplay:
3. You must return all attached DON!! to the DON!! Area in the Refresh Phase.
4. When a Character's Power is reduced to 0 it is not destroyed.
5. DON!! x # effects activate even if you have more than the designated number of DON!! attached.
6. Different cards with the same name can each activate their [Once per turn] effect.
Replacing Characters:
7. If you have 5 Characters on the field, you must send 1 of them to the trash when you play another one, and the Character sent to the trash does not activate its [When K.O.] effect.
Counter Rulings:
8. You cannot use Characters on the field to Counter, you can only use Counter from cards on your hand.
9. If being attacked, you can also use Counter to boost the Power of Characters not battling, but their effects last until the end of the battle you used them in.
10. You do not pay the Play Cost of a Character when using it as a Counter
On Play Rulings:
11. You must activate a Character's [On Play] effect when played, unless it has a cost, in which case you can choose to activate it or not.
Blocker Rulings:
12. It's not mandatory to activate [Blocker] when attacked, but if you do you can only activate [Blocker] once per attack.
13. You cannot activate [Blocker] if that Character is the target of the attack.
14. You can boost the Power of a card that use [Blocker] with Counters.
Banish Rulings:
15. You must send the Life cards to the trash if you deal damage with a Character with [Banish].
Double Attack Rulings:
16. You must deal 2 damage if you successfully deal damage with a Character with [Double Attack], even if you lose the effect or the attacker is removed.
17. You do not win if you deal damage with a Character with [Double Attack] and your opponent only has 1 Life.
Trigger Rulings:
18. You can choose to not activate [Trigger] and add that card to the hand instead.
Action during Battling:
1. Attack Step: Rest one of your Characters or Leader to attack your target (Can be opposing Leader or a rested opposing Character).
If there's [When attacking] effects, they will activate as soon as you declare your target.
2. Block Step: The attacked player can activate one of their Characters [Blocker]
3. Counter Step: The attacked player can activate as many cards with [Counter] from their hand as they can.
4. Damage Step: Compare the power of the attacking card with the power of the attacked card. If the power of the attacking card is greater than or equal to the power of the attacked card, you will win the battle and the result will depend on the attacked card.
(If you attack your opponent's Leader, inflict 1 damage on the Leader who lost the battle. If attacking a Character, KO the character who lost the battle and put it in the trash. If the attacking card loses, nothing happens.)
When your leader is damaged, add 1 card from your life to your hand.
At this moment, if the card has a [Trigger] effect, you can reveal the card and activate the [Trigger] effect.
Also, if the leader is damaged and there's no more life cards for him, that player loses the game.