Marucho Marukura, nicknamed Marucho, comes from immense wealth and initially displays extreme obedience to his parents out of fear. This changes after joining the Battle Brawlers, though he keeps his respectful nature. He speaks formally in the Japanese version, using honorifics like "Dan-san" and "Drago-san". Introduced as an 11-year-old Aquos brawler, he moves near Dan Kuso. His guardian Bakugan, Preyas, dramatically crashes his housewarming party, beginning their partnership. During a clash with Klaus von Hertzon, Preyas is banished to the Doom Dimension. Driven by fierce determination, Marucho pursues Klaus through a portal to save him. Later, Dan and Runo Misaki help reclaim Preyas using Pure Light. Preyas then evolves into Angelo/Diablo Preyas, granting Marucho both forms as partners. Marucho faces a significant trial when an illusion of his former obedient self confronts him. He accepts his past, acknowledging his desire to please his parents shaped him, allowing him to pass. He participates in crucial battles, including team efforts with Shun Kazami against hybrid Bakugan like Tayghen and Hairadee, employing strategic elemental combinations. He aids in the final conflict against Naga before releasing his Bakugan. In *New Vestroia*, now 13, he secretly follows Dan and Drago to help New Vestroia against Vestal invaders. Disappointed by his lack of an Aquos partner early on, he discovers Elfin in a jungle. After teaming up to repel Mylene Farrow and protect the Aquos Bakugan Wontu, Elfin becomes his new partner, revealing she trained under Preyas. Shun rescues them during this event. Elfin later evolves into Minx Elfin. Marucho secures key victories, such as defeating Shadow Prove to unblock a portal, and contributes to missions like destroying Dimension Controllers. Captured and later freed by Mira and Spectra Phantom, he eventually reunites with Preyas. Post-crisis, Akwimos becomes his primary partner for the next season. During *Gundalian Invaders* (age 15), Marucho creates Bakugan Interspace using Phantom Data provided by Ren Krawler, enabling global brawling. Ranked #3 in Interspace, he gifts Jake Vallory a digital Subterra Coredem. He initially believes in Ren's innocence despite betrayal suspicions, battling him to uncover the truth. His strategic brilliance shines when devising decoy tactics in the Gundalian-Neathian war, earning Queen Serena's praise as a "gift to Neathia." Emotional turmoil during a battle against Ren and Nurzak triggers a Sacred Orb warning, but he later reconciles with Ren. He faces losses against opponents like Stoica and Gill, utilizing Aquos Akwimos and Battle Gear Gigarth. In *Mechtanium Surge* (ages 16-17), his partners include Aquos Infinity Trister (with Mechtogan Accelerak and BakuNano Silver Crosstriker) initially, then Aquos Radizen (with Mechtogan Flytris) plus a temporarily borrowed Subterra Roxtor from Mira Fermin. He adopts multi-attribute battling, combining Aquos and Subterra to form Betakor. He duels Shun and confronts antagonists like Anubias and Mag Mel alongside the Brawlers, utilizing Battle Suits such as Aquos Blasterate and Clawbruk. Throughout the series, Marucho serves as the Battle Brawlers' tactician, renowned for his strategic mind and encyclopedic Bakugan knowledge. His journey reflects increasing confidence and leadership, transforming from an obedient child into a resilient warrior instrumental in saving multiple worlds.