Following the game's release, five more One Piece games would be produced for WonderSwan consoles, though Become the Pirate King! remains the only one compatible with the original monochromatic system.
The game mainly revolves around path-building, with players laying tiles across various sea maps. The piecemeal paths depicted on these tiles must be connected so players can reach objectives such as islands and enemy crews.
Tiles come in four basic path formations - straights, elbows, T's, and crosses - that can be rotated clockwise or counterclockwise in 90-degree intervals. A tile's "strength" is determined by its texture; dark tiles (carrying "padded" rivets) can be replaced by new tiles, while light tiles (carrying "bolted" rivets) cannot.
Players are limited to a pool of five tiles at any given time. After a tile has been laid, its successor must be chosen from a randomly shuffled "deal" of five new tiles.
Exploration mainly relies on the Move (移動 Ido?) command, which opens the player's current tile pool and (if applicable) replacement shuffle. One tile must be laid every turn, though it need not be connected or even adjacent to any other tiles.
After laying the tile, the player will be granted a Jolly Roger marker to plot their destination, and a number of movement points equal to the number on the tile; each rivet on a path costs one movement point to cross. Once the destination is set, the player will automatically sail there, ending the current turn.
Note that "leftover" movement points cannot be carried between turns; every new turn will start with zero movement points.
Combat employs many of the same tile mechanics as exploration. Players may field a maximum of three combatants, and lay up to three tiles per round.
The combat map proper is a 3x3 grid, with the battling crews on opposite ends. The top and bottom rows of this grid are pre-laid with identical paths; to reach the enemy, each side must build a functional path through the middle row. While movement points do not exist in combat, the numbers on the tiles are still vital for determining initiative; whichever side compiles the higher sum lays - and attacks - first.
Once the tiles are laid, the combatants will move according to their lineup positions: the rightmost character will take the rightmost route, and the leftmost character the leftmost route, and the center character the center route. This lineup may be reordered at the start of every round, alongside tile selection.
Each character is assigned a Type (タイプ Taipu?), which governs their attack capabilities:
- Melee (近距離 Kinkyori?) types, such as Zoro, must reach the far row to attack. On reaching the far row, they will attack the character in the closest square; if this square is unoccupied, they will attack the enemy ship instead.
- Ranged (遠距離 Enkyori?) types, such as Usopp, must stop at the middle row to attack. Unlike Melee types, they can only attack the enemy ship.
- Adept (万能 Ban'nō?) types, such as Luffy, may employ both Melee and Ranged attacks.
Combat performance relies on the following attributes:
- Offense (攻撃力 Kōgeki-ryoku?), which determines the "raw" damage dealt by a successful attack.
- Defense (守備力 Shubi-ryoku?), which determines the damage deducted from an enemy attack; if high enough, it can completely nullify an attack.
- Agility (素早さ Subaya-sa?), which determines what order a given side's combatants will attack in.
In addition, every character has several Finisher (必殺 Hissatsu?) attacks tied to unique path formations - Luffy, for instance, will perform a Gomu Gomu no Bazooka if facing a cross between two vertical straights. A successful finisher will always deal a fixed amount of damage to every enemy combatant and ship, but also lock any allies out of attacking until the next round.
A combat is won when the enemy crew has lost every member, or their ship.
There are thirty-six playable characters, comprising almost every notable figure from the East Blue Saga.
Outside of combat, players may use - or discard - a number of items via the Inventory (道具 Dōgu?).
|Mikan (ミカン?)||Restores 10 HP to one chosen character.|
|Raw Ham Melon (生ハムメロン?)||Restores 15 HP to one chosen character.|
|Bean Stirfry (もやし炒め?)||Restores 20 HP to one chosen character.|
|Drumstick (骨付き肉?)||Restores 30 HP to one chosen character.|
|Pirate Bento (海賊弁当?)||Restores 40 HP to one chosen character.|
|Lumber (木材?)||Restores 30 HP to the ship.|
Items are typically obtained - at random - from combat victories and other significant events. Note that the Inventory can hold a maximum of ten items.
Four different modes may be accessed from the Top Menu, including several multiplayer modes able to support up to four players.
Note that none of the multiplayer modes support play via the WonderSwan's link-cable system. Instead, a single WonderSwan console must be passed back and forth between players.
The Solo (おれがあそぶ Ore ga isobu?, lit. "I'll play") mode adapts the Straw Hat Pirates' East Blue adventures into six levels of exploration and combat. Each level contains a mixture of combat and racing missions, interspersed with scenes and dialogue adapted directly from the manga.
After a level has been cleared, it may be played again any number of times. Most of the enemies in a level can be unlocked as playable characters if a re-play is finished within a set number of turns.
| Morgan Arc|
| Buggy Arc|
| Black Cat Arc|
| Krieg Arc|
| Arlong Arc|
| Loguetown Arc|
| El Drago Arc|
The Multi-Player (みんなであそぶ Min'na de asobu?, lit. "everyone plays") mode allows players to assemble custom crews and race each other across eight separate maps. Its combat and sailing mechanics are mostly identical to those of Solo mode, although players cannot see enemy ships until they occupy adjacent tiles. Combat initiates whenever two ships meet on the same tile, and is limited to one round in all circumstances.
In addition, players may access several "support" tiles that offer no paths or movement points, instead laying traps or exercising other special effects on the sailing map:
- Tailwind (追風 Oikaze?) tiles double the movement points on the next two tiles the player lays.
- Headwind (向風 Mukaze?) tiles halve the movement points on the next two tiles every opponent lays (rounding up for odd values).
- Cannon (砲 Hō?) tiles allow the player to shoot one tile within a 5x5 area, destroying any path it contains; any player occupying the shot tile will be capsized, skipping their next turn.
- Rock (岩 Iwa?) tiles capsize the first crossing player, skipping their next turn.
- King (王 Ō?) tiles ambush the first crossing player with a Sea King, skipping their next turn.
- Whirlpool (渦 Uzu?) tiles send the first crossing player to a random point on the map.
All support and trap tiles can also be laid on the combat map, inflicting a flat amount of damage on the first character to cross.
Reaching any of the checkpoint islands scattered throughout the Multi-Player maps will prompt one of three possible mini-games.
- Big-Eater Blowout (大食い競争 Ōkui kyōsō?), which randomly selects one character from each player's crew to compete in a Baratie eating contest. Each competitor has 30 seconds to grab as many dishes as possible (taking care to avoid those contaminated by flies).
- Mihawk's Diversion (ミホークのひまつぶし Mihawk no himatsubushi?), which randomly selects one character from each player's crew to battle Mihawk. Competitors take turns attacking Mihawk under a set of nim-like conditions, trying to maneuver each other into making the final attack.
- High-Seas Showdown (海上大決戦 Kaijō daisakusen?), which pits every player's crew against a combined assault from Fullbody, Nezumi, and Pudding Pudding. Competitors take turns shooting a fleet of thirty Marine ships, trying to sink them all before any can cross a designated dead zone.
An electronic adaptation of the Carddass Hyper Battle system attached to the official One Piece card game. Supports up to four players.
- The Solo mode depicts the Going Merry as Luffy's ship from the very beginning, rather than an acquisition from Syrup Village.
- On its initial release, the game's instruction booklet was packaged with six exclusive Carddass cards, all based on the game's box-art. One used the box-art directly, while the other five depicted the individual Straw Hat Pirates.
- ↑ Ripper's portrait stands in for several other minor Marines - such as Lines - in subsequent levels.
- ↑ Poppoko's portrait stands in for several other minor pirates - such as the Superhuman Domingos - in subsequent levels.
- ↑ Completing Solo mode will also cause a special "Panda Island" to be hidden inside every level, to be discovered on re-play. Discovering all seven Panda Islands will unlock Pandaman as a playable character.