Marucho Marukura (also known as Choji Marukura) is a primary Aquos brawler for the Battle Brawlers throughout the series. Born into wealth, he initially obeys his parents out of fear, a trait evolving after joining the team. He serves as the team's analytical and strategic mind, communicating with notable politeness and formality, including honorifics in Japanese. His Guardian Bakugan partnerships evolve across seasons. Preyas is his initial partner in *Bakugan Battle Brawlers*. After confinement in the Doom Dimension, Preyas evolves into Angelo/Diablo Preyas, a dual-form entity: Angelo (Aquos-Haos, polite) and Diablo (Aquos-Pyrus, aggressive). In *New Vestroia*, Preyas is captured by Vestals, leading Marucho to partner with the Aquos Bakugan Elfin, who later evolves into Minx Elfin. Akwimos becomes his primary partner during *Gundalian Invaders*. *Mechtanium Surge* features partnerships with Infinity Trister (Arc 1), Radizen, and a temporary borrowing of Mira Fermin's Subterra Roxtor (Arc 2), utilizing the Aquos/Subterra fusion Bakugan Betakor. Significant development occurs throughout his journey. During *Bakugan Battle Brawlers*, he confronts and accepts a psychological manifestation of his former obedient self during Frosch's test. He participates in key team battles against Tayghen, Hairadee, and Naga. In *New Vestroia*, he follows Dan Kuso and Drago into Vestroia without authorization, joining the Resistance. Initial insecurity over lacking an Aquos partner resolves upon partnering with Elfin after battling Mylene Farrow. He secures strategic victories against Shadow Prove to unblock portals and at Gamma City enabling the Dimension Controller's destruction, though suffers losses to Volt Luster leading to temporary captivity. He provides residential support at his shielded mansion upon the Resistance's return to Earth. During *Gundalian Invaders*, he develops Bakugan Interspace using Phantom Data, achieving global rank #3. He devises decoy operations protecting Neathia's Second Shield, earning Queen Serena's recognition. He experiences emotional conflict confronting Ren Krawler's betrayal but maintains belief in Ren's inherent goodness. *Mechtanium Surge* sees him adapt to BakuNano, Mechtogan, and Battle Suit mechanics, forming Ventus/Aquos Duomechtra combinations with Shun Kazami. Marucho demonstrates consistent loyalty to core teammates Dan Kuso and Shun Kazami. His butler, Kato, serves him early on before reassigning to his father. He interacts with Jake Vallory, providing Subterra Coredem and battling collaboratively. Conflict with Ren Krawler resolves through renewed trust. His Bakugan partnerships involve mutual growth, evident in testing prototypes like JetKor with Keith Fermin. His battling techniques leverage Aquos attribute fluidity, alternating between support and aggression, and emphasize multi-attribute coordination. Key victories include collaborative defeats of the Alternative Weapon System and various Gundalian commanders. Losses occur against opponents like Stoica and Gunz Lazar. His battle record shows evolving competence, with increasing technological adaptation in later arcs.