Masato is the younger son of Petalburg City's Gym Leader and his wife in Hoenn. An intelligent child, he commands an extensive, almost encyclopedic knowledge of Pokémon species, abilities, and battle strategies, primarily gained from books and data. This deep knowledge can initially manifest as behavior perceived as arrogant or know-it-all, especially towards less experienced trainers. He deeply admires his father's strength as a Gym Leader but harbors complex feelings about his own future as a trainer, expressing both a desire for strength and moments of hesitation or self-doubt about meeting expectations. Masato often displays a mischievous side, particularly teasing his older sister, Haruka, regarding her initial lack of Pokémon interest and knowledge. Despite this sibling rivalry, a strong bond exists, and Masato is fiercely protective of Haruka. Traveling alongside Haruka and Satoshi drives significant growth. Initially critical of Satoshi's battling style, Masato gradually develops respect for Satoshi's intuition and connection with Pokémon, learning that practical experience and heart are as vital as book knowledge. This journey exposes him to the realities of being a trainer, nurturing empathy and understanding beyond theory. He forms strong friendships with the Pokémon traveling with the group, especially Haruka's Skitty. A pivotal experience occurs during the Millennium Comet festival. Masato encounters the Mythical Pokémon Jirachi, quickly forming a deep, genuine friendship. He sees beyond its wish-granting power to the lonely being beneath. Masato selflessly protects Jirachi from those seeking to exploit it, sharing simple joys and offering comfort. Witnessing Jirachi's cyclical thousand-year awakenings and returns to deep sleep teaches him profound lessons about the transient nature of powerful moments and the enduring value of true friendship and memories, even when separated. Through these experiences, Masato matures significantly. His intellectual arrogance diminishes, replaced by a more balanced perspective valuing emotional bonds and practical wisdom alongside factual knowledge. His protective instincts strengthen, and his resolve to become a skilled Pokémon trainer in his own right solidifies, shaped by the compassion and resilience learned on his journey and from his unique bond with Jirachi.