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The Reverse Mountain Arc, also referred to as the Laboon Arc, is the first story arc of the Arabasta Saga in the manga and anime, One Piece.

In this arc, the Straw Hat Pirates make their way to Reverse Mountain and begin the perilous task of scaling its tricky rapids in order to enter the Grand Line. As they descend the mountain, they find that something huge is blocking the entrance.


A Giant Whale and a Mysterious Duo

As the Straw Hats sail through a storm, Nami realizes that they will be going up Reverse Mountain to access the Grand Line. The crew expresses disbelief at the idea, with Zoro wondering why they can't just go south. Suddenly, the storm stops, and Nami reveals that they are in the Calm Belt, one of two strips of ocean surrounding the Grand Line, where there are no winds or currents. Nami urges the crew to row back to the storm, but the Sea Kings infesting the water then rise up. The Straw Hats struggle to get away, and once they escape, they turn their attention to successfully riding the dangerous current up Reverse Mountain. Their rudder soon breaks, but Luffy shields the Going Merry from hitting the mountain as the Straw Hats successfully sail down into the Grand Line.[1]

Laboon blocking the Straw Hat Pirates' path.

When they come down, they immediately run into a giant whale named Laboon, who is blocking their path. The Merry ends up running into the whale, which breaks its masthead. Luffy punches Laboon in the eye in retaliation for his seat being destroyed. Laboon then opens his mouth, swallowing the Going Merry, although Luffy manages to escape. Luffy tries hitting Laboon to get his friends out, but before the whale dives underwater, he spots and enters a trapdoor on the whale's back. Meanwhile, the other Straw Hats find themselves sailing towards an island inside Laboon. They soon encounter a giant squid,[2] which is taken down by a man named Crocus. After an initially tense confrontation, Crocus points them toward an escape route.[3]

Right then, Laboon begins ramming himself into Reverse Mountain, causing further injuries to his head. As this happens, two mysterious people named Mr. 9 and Miss Wednesday prepare to take Crocus out to Laboon and use him to feed the people of their town. However, Luffy is sent tumbling through the corridors by Laboon's thrashing, and he ends up crashing into Mr. 9 and Miss Wednesday, sending them flying into the area where the Straw Hats and Crocus were. Crocus went to calm Laboon down before confronting the two rogues, and took two bazooka shots aimed at Laboon as Luffy defeats the rogues. They return to Crocus' island, where Crocus explained about Mr. 9 and Miss Wednesday to the Straw Hats. He then revealed that Laboon had come to the Grand Line with a pirate crew, and was asked to stay with him at Reverse Mountain as the crew could not risk taking the whale with them. Over 50 years had passed since then, but Laboon still believed that the crew would come back.[3] The Straw Hats exited Laboon's body, and threw Mr. 9 and Miss Wednesday into the water. The two agents swore revenge on the pirates before swimming away. At Twin Cape, Crocus revealed that he had heard that the crew with Laboon had not died, but rather had left the Grand Line. He told this to Laboon, but the whale seemed to refuse to believe him and started ramming his head against Reverse Mountain, as though trying to get to the crew.[4]

Luffy looks at the Log Pose he found.

Right then, Luffy took the Merry's mast and plunged it into one of Laboon's open wounds, causing the whale to lash out against him. The two traded blows, and Luffy proclaimed that he was now Laboon's rival, promising to see and fight him again once his crew sailed around the Grand Line.[4] This made Laboon happy, and Luffy painted his Jolly Roger on the whale's forehead, telling him not to bash his head against the mountain any longer. Meanwhile, Nami was shocked as her compass stopped working. Crocus tells Nami that to navigate the Grand Line, one would need a Log Pose to chart the differing magnetic fields of each island, all the way to the last island Laugh Tale. Luffy had acquired a Log Pose that Mr. 9 and Miss Wednesday had left on the Merry, but it ended up breaking when he and Sanji got in a fight. However, Crocus agreed to give them a Log Pose out of gratitude for helping Laboon.[5]

Meanwhile, Mr. 9 and Miss Wednesday swam up to the Twin Cape to try to get their Log Pose back, as they needed to get back to their island and report to their boss before they got into trouble. However, the Unluckies then came to try and kill them. After recovering from the attack, the two rogues went to the Straw Hats and asked them to take them to Whisky Peak. They were unable to divulge their identities, but the Straw Hats reluctantly agreed to help. They then set sail for Whisky Peak, bidding farewell to Crocus and Laboon, and Crocus wondered if Luffy was the one he and Roger had been waiting for.[5]

Story Impact

  • The Straw Hats make it to the Grand Line.[1]
  • The Straw Hats meet a whale called Laboon, and Luffy agrees to reunite with him after making it across the Grand Line.[4]
    • Laboon is revealed to be waiting for a crew that left him 50 years ago. The Straw Hats will go on to meet one of that crew, who will join them to fulfill the promise his crew made.[3][4]
  • The Straw Hats agree to take two mysterious rogues to their home island of Whisky Peak. One of the two rogues and their organization will drive the Straw Hats' actions through the rest of the Arabasta Saga.[5]
  • Information about the Grand Line and the Calm Belt is revealed.
    • The Calm Belt is a sea surrounding the Grand Line which has no winds and is infested with Sea Kings. It is very difficult, but not impossible, to traverse.[1]
    • The Log Pose is introduced, which helps sailors navigate the Grand Line due to its islands carrying their own distinct magnetic fields. The Straw Hats gain a Log Pose.[5]
    • The location of One Piece is on an island known as Laugh Tale.

Anime and Manga Differences

Exiting Laboon

The episodes concerning the arc were heavily edited, and much of the arc was completely omitted in the 4Kids dub.

Manga: When the Straw Hats manage to reach Laboon's "exit", they simply throw the Mr. 9 pair off the ship, who then wake up in the ocean.

Anime: The Mr. 9 pair manage to escape on their own, without the Straw Hats noticing them.

Warship Island Arc

Manga: After the Straw Hat crew leaves Loguetown, they first reach the Calm Belt, and then head to Reverse Mountain, where they travel up the canal to enter the Grand Line.[6]

Anime: After the Straw Hat crew leaves Loguetown, they find a girl in the ocean and rescue her. They then head to Warship Island, leading to a filler arc.[6]

Discussing Reverse Mountain

Manga: After the Straw Hat pirates leave Loguetown, while passing the lighthouse, they begin to discuss how to enter the Grand Line. During the meeting, the ship drifts out of the storm into the Calm Belt. The weather is stormy and Nami wears her raincoat until after they get to the top of the mountain.[6]

Anime: The whole discussion is moved to the last episode, and there is no drifting into the Calm Belt due to having been shown in the second filler episode. It is not very stormy and Nami is not wearing her raincoat.[6]

Calm Belt

Manga: Nami talks about it after they see a bunch of Sea Kings and the Going Merry is on a giant Sea King's nose.[7]

Anime: Nami explains the Calm Belt upon reaching it (after the rest of the Straw Hats show that they do not know about it).[7]

Calm Belt 2

Manga: The Calm Belt does not take place during the Warship Island Arc and Apis is not with the pirates. Luffy saves Usopp when he gets tossed off the ship and is about to be eaten by a Sea King.[7]

Anime: The whole Calm Belt situation is moved to the third episode of the Warship Island arc, Apis is with them, and Luffy saves her from the Sea King instead of Usopp.[7]

Steel Cutting

Manga: Zoro is not supposed to be able to cut steel until the Arabasta arc.[8]

Anime: Zoro cuts the steel chain from the Marine ships. He even says "There is nothing I cannot cut". This becomes one of the major plot holes in the anime series.

Note: After Luffy is declared wanted, Zoro is the one who cuts the cannonball in two fired at them by Fullbody.[8]

Hello Eric

Manga: The Straw Hat Pirates go up Reverse Mountain without anyone interrupting them.[8]

Anime: As the Straw Hat Pirates go up Reverse Mountain, Eric lands on the Going Merry, yet he is later tripped by Nami and falls off the ship into the sea.[8]

Translation and Dub Issues

4Kids has cut and changed much of the arc for unknown reasons, but it may be due to Laboon's scars and Luffy stabbing the Merry's mast into his head. The Straw Hats entering the Grand Line and receiving the Log Pose is rewritten as a result, and shots from other segments of the anime are rearranged to fit the script:

  • Rather than confronting Laboon, the Straw Hats instead encounter an iceberg in their way, which Luffy destroys with the ship's cannon. In the Japanese version, he fires it to slow the Going Merry down and keep it from crashing into Laboon.
  • The Log Pose suddenly appears onboard the ship, and the explanation of how it works and the physics of the Grand Line are told through flashbacks by the crew when they were children instead of by Crocus, whom they never meet in the 4Kids dub. Yet until the Sabaody Archipelago Arc, we end up learning more about Crocus which creates more problems.
  • Without Crocus, the Straw Hat Pirates never knew anything about Laugh Tale and how this would come to play in the Zou Arc when he gets brought up when discussing the island with Zou's rulers
  • The Straw Hats arrive at Whisky Peak (renamed Misty Peak) on their own rather than being led there by the Mr. 9 pair.

Because of these changes, many fans have expressed outrage and disapproval at 4Kids for creating something that was obviously not part of the author's original canonical storyline, and also expressed concern for Brook's plot in the American dub.

However, with the 4Kids dub cancelled and FUNimation now dubbing the series, the Reverse Mountain Arc saw its first English anime release on June 30, 2009 as part of FUNimation's uncut "One Piece Season 2 First Voyage" release.



  1. 1.0 1.1 1.2 One Piece Manga — Vol. 12 Chapter 101.
  2. One Piece Manga — Vol. 12 Chapter 102.
  3. 3.0 3.1 3.2 One Piece Manga — Vol. 12 Chapter 103.
  4. 4.0 4.1 4.2 4.3 One Piece Manga — Vol. 12 Chapter 104.
  5. 5.0 5.1 5.2 5.3 One Piece Manga — Vol. 12 Chapter 105.
  6. 6.0 6.1 6.2 6.3 One Piece Manga and Anime — Vol. 12 Chapter 101 and Episodes 5355.
  7. 7.0 7.1 7.2 7.3 One Piece Manga and Anime — Vol. 12 Chapter 101 and Episode 55.
  8. 8.0 8.1 8.2 8.3 One Piece Manga and Anime — Vol. 21 Chapter 193 and Episodes 5961.

Arc Navigation

Reverse Mountain Arc
Manga Chapters
101 102 103 104 105
Manga Volumes
Anime Episodes
62 63

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