Choji "Marucho" Marukura is a core Battle Brawlers member across all seasons, specializing in Aquos. Introduced at age 11, he ages to 13 in New Vestroia, 15 in Gundalian Invaders, and 16-17 in Mechtanium Surge. Hailing from wealth, his initial obedience to parents stemmed from fear, but joining the Brawlers fostered greater independence while retaining respect. He serves as the team's strategic intellect, often called a "walking encyclopedia" for his vast knowledge and passion for devising battle tactics. His philosophy centers on water's adaptable power, valuing its capacity for both gentle and forceful expressions. His primary partner is Aquos Preyas throughout Battle Brawlers and New Vestroia, though Vestals capture Preyas early in New Vestroia. Searching for a new Aquos Bakugan leads him to partner with Aquos Elfin; Elfin evolves into Minx Elfin after receiving energy from the Six Ancient Warriors. He reunites with Preyas in New Vestroia episode 26, resulting in both Bakugan vying for his partnership. Later partners include Akwimos in Gundalian Invaders, Infinity Trister in Mechtanium Surge's first arc, and Radizen alongside the borrowed Subterra Roxtor from Mira Fermin in the second arc. He also utilizes BakuNano like Silver Crosstriker, Mechtogan such as Flytris and Accelerak, and Battle Suits including Blasterate and Clawbruk. In New Vestroia, he travels with Dan Kuso to aid the Resistance against Vestal occupation. Key battles involve an initial loss to Vexos member Mylene Farrow while testing his partnership with Elfin, a victory against Shadow Prove securing a portal, a deliberate loss to an unknown brawler, and a loss to Volt Luster leading to temporary captivity. He later achieves significant wins, including a tag-team victory with Shun Kazami against Mylene and Shadow Prove at Gamma City, and participates in the final battle against King Zenoheld. He contributes strategically to Resistance efforts, like helping destroy Dimension Controllers to liberate Bakugan. His role expands beyond battling in later arcs. During Mechtanium Surge, he assumes temporary leadership of the Battle Brawlers following internal conflicts involving Dan Kuso and Shun Kazami, eventually relinquishing the role back to Dan. He partners with Mira Fermin to establish Bakugan City, utilizing Vestal technology to create a new brawling environment after Bakugan Interspace's collapse. He confronts challenges from rogue Mechtogan and the Chaos Army, participating in large-scale battles to protect the city. His character consistently leverages intellect and adaptability, forming new partnerships and employing strategy against evolving threats.