Masachika Kōda, an eighth dan professional shogi player, serves as Rei Kiriyama's adoptive father and primary shogi mentor. He shared a close friendship and rivalry with Rei's biological father during their early years in the Shogi Training Group. Following the traffic accident that claimed Rei's parents and sister, Masachika adopted Rei into his home, raising him alongside his biological children Kyōko and Ayumu. He formally trained Rei as his shogi apprentice to guide him toward professional play.

Masachika approaches shogi with intense seriousness, enforcing strict discipline in training and competition—a philosophy that shaped his parenting. He initially pressured Kyōko and Ayumu to pursue shogi as rigorously as Rei, frequently comparing their abilities. After determining they lacked competitive instincts—such as failing to detect Rei's deliberate match losses—he forced both to quit the Shogi Training Group. This decision triggered lasting consequences: Kyōko abandoned her ambitions and later entered an affair with an older shogi player, while Ayumu retreated into reclusiveness and video games.

His preferential treatment of Rei, driven by recognition of Rei's prodigious talent, cultivated hostility within the household. Masachika's focus on Rei's development overshadowed Kyōko and Ayumu's emotional needs, fueling their resentment toward Rei. This dynamic prompted Rei to leave after middle school, believing his presence fractured the family. Despite the separation, Masachika managed Rei's shogi earnings until adulthood and maintained periodic contact, reflecting his underlying concern for Rei's well-being and education.

Masachika grapples with guilt over the family's disintegration, acknowledging his shogi-centric focus and insufficient emotional support contributed to his children's struggles. Though he struggles to express care directly, he remains quietly involved—managing Rei's finances and worrying about Rei's school isolation. In shogi circles, he commands respect for his expertise, including televised matches against elite players like Tōji Sōya.

His name combines the kanji for "happiness/good luck" (幸) and "field/rice paddy" (田) in Kōda, with "straight grain/spindle tree" (柾) and "near/akin" (近) in Masachika, reflecting traditional values. The live-action film adaptation formally established this name and featured a flashback of his match against Sōya.