Magoichi hails from distant Nanban Ispania, distinguished by blonde hair and blue eyes—the latter an innate Dragon Eye. Shipwrecked, he washes ashore near Saikazaki with complete amnesia and is taken in by villagers. They name him "Magoichi" after a local hero, integrating him into their community. As part of the Saika Ikki mercenary group, he masters specialized "armors," weapons granting enhanced combat prowess. His exceptional skill and natural leadership propel him to lead the group. He customarily wears red attire bearing the Saika emblem on the back.

Confident and level-headed, Magoichi possesses a fierce protective instinct for the village and its people. This drive is tested during repeated invasions targeting Saika. While he repels initial attacks, stronger subsequent foes overwhelm him. A critical confrontation brings not only physical defeat but profound emotional turmoil triggered by a masked figure in armor, leading to an intervention by an unknown rescuer.

A hidden aspect of his past involves his familial bond with Lucio Cortes, revealed as his brother. Before his amnesia, Magoichi played a pivotal role mentoring Lucio, instructing him in combat techniques and power usage—instruction that ultimately contributed to Lucio's descent into ruthlessness and widespread destruction across nations. As Magoichi recovers fragmented memories throughout the series, guilt and responsibility for Lucio's actions burden him. This fuels his determination to confront and rectify the consequences of his past influence, directly opposing Lucio's destructive ambitions.

His narrative arc centers on relentless efforts to protect the village while confronting his forgotten past's legacy. Internal conflict from amnesia and external threats, including his brother, drive his development. His journey involves reconciling his identity as Saika's current protector with revelations of his pre-amnesia life and complex familial bond with Lucio.