Marine Rookie Arc

The Marine Rookie Arc (海軍超新星（ルーキー）編), or the Fron Island Arc, is the thirteenth filler arc and the fourth filler arc after the timeskip.

After running out of food on the way to Whole Cake Island, the Sanji Retrieval Team sneaks into a Marine base to steal some.

Summary
The Sanji Retrieval Team was famished due to Luffy wasting all their supplies, but they came to an island that Nami had saw on the map in Zou. They prepared to look for food there, but Pekoms warned them that the island, Fron Island, was home to a Marine base that kept an eye on Big Mom. Luffy, Nami, Chopper, Carrot, and Brook then headed to the island on the Shark Submerge III while Pedro and Pekoms stayed behind to guard the Sunny.

On Fron Island, Vice Admiral Prodi watched as a ship carrying reserve forces drew near to the island. However, the ship suddenly erupted into chaos as Grount, a 17-year-old Captain, started attacking his comrades. Grount easily overpowered his comrades with his tremendous power and reported to Prodi that they were all weak, angering the vice admiral. Prodi took Grount to his office and called Garp to find out why Grount was transferred here. He discovered that Grount requested to be stationed here in order to take down Big Mom, and dismissed that dream before angering Grount further by belittling Aokiji, his former commander.

The Straw Hat Crew knocked out a group of Marines and stole their clothing, and Brook went back to the Shark Submerge III while the rest prepared to raid a food storage building. However, Luffy and Carrot went to a cafeteria, where they were served food. Grount went to the cafeteria as well, where he reunited with his old comrades under Aokiji, Bonam and Zappa. Nami and Chopper then entered the cafeteria, and Carrot called Nami's name, causing Zappa to notice her. Zappa approached Nami and proposed to her, but Nami ran away, leaving him sullen again. Meanwhile, Prodi found out about the Marines the Straw Hat Crew attacked and activated an alarm as he and his forces searched for the intruders. When Luffy caused an altercation in the cafeteria by taking an entire bowl of curry, Prodi spotted him, and ordered his men to battle against the Straw Hat Crew. As this happened, Nami and Chopper ran to the storage building to get more food rations, while Brook, Carrot, and Luffy were all surrounded by Marines. An excited Grount then prepared to fight Luffy.

Luffy was uninterested in fighting and tried to leave, but Grount lunged at him and Luffy countered his daggers with the curry ladle. The two dueled, but Luffy got the better of Grount by slamming the bottom of the ladle into the Marine's face. Bonham then stepped in and attacked Luffy with rapid Rokushiki moves, but Luffy managed to avoid all of them and he tried to leave the room. Bonham blocked the exit and activated Tekkai, but Luffy activated Gear Second and blew him away. Luffy and Carrot ran down the hall, but were approached by Zappa, who tried to woo Carrot. Zappa got jealous of Luffy and tried attacking him, but Luffy blocked his attacks before Carrot knocked him down with Electro. Luffy and Carrot were then approached by Brook's detached soul, and they raced to reunite with Nami and Chopper with Grount, Bonham, and Zappa in hot pursuit. Brook led them to a dead end, and Grount and Bonham cornered the trio. However, they argued over who would get to take down the intruders, allowing Luffy to punch a hole in the wall and allow him and Carrot to escape.

Luffy and Carrot raced to the food storage facility where Nami and Chopper were, and they started gorging on food. They reunited with Nami and Chopper, but the group was quickly confronted by Grount, Bonham, and Zappa. Chopper took on Bonham in combat, but was initially overpowered by Bonham's Rokushiki. However, he managed to block Bonham's attacks with Guard Point, before activating Heavy Point and blowing Bonham away despite him using Tekkai. Zappa continued to try and woo Nami and Carrot, and attempted to take down Luffy so he could have the ladies to himself. Both Carrot and Nami struck him with electric attacks, but Zappa refused to stay down as his swords caught fire and he unleashed a giant fiery whirlwind at Luffy. However, Luffy redirected the attack at a giant pot of water above them, causing it to crash down on Zappa and flood the facility. The Sanji retrieval team was washed outside, and just as they tried to escape they were confronted by Grount. Luffy brawled with Grount and eventually got the upper hand, sending a bloody Grount sprawling on the ground. As Bonham and Zappa returned and tended to Grount, the team tried to escape once more, but when they got to the coast, they were confronted by Prodi, who was determined to take them down in order to avoid getting demoted.

Trivia

 * This is the second filler arc in which Luffy and his group infiltrate a Marine base, the first being the G-8 Arc.