Hiiro Ryugasaki, a second-year student at Tensei Academy, begins as an unassuming middle schooler with a fervent passion for the Shadowverse card game. His life transforms upon discovering a mysterious smartphone housing the game, which unveils its true intent: thwarting a global catastrophe tied to the Tree of Woe—a failed invention by his father’s company that trapped his parents. This revelation fuels his resolve to master Shadowverse and protect others from impending ruin.

Initially specializing in Dragoncraft, he harnesses Overflow mechanics to strengthen his followers, his relentless perseverance forging rivalries and alliances through tournaments. These battles redefine Shadowverse as more than a game, framing it as a crucial defense against existential threats.

Three years later, he joins the Seven Shadows, an elite group founded by Luca Yonazuki to recruit protectors and combat crises under Genesis Corporation’s sponsorship. Investigating the enigmatic Arc artifact and repelling Shade invasions, Hiiro adopts Portalcraft, broadening his tactical range. The group’s mission to dismantle the Arc Ruler’s genocidal scheme falters as betrayals fracture their ranks, exposing conflicting personal agendas.

Hiiro’s past, marked by the belief that his parents died in an accident, gains complexity when he learns of their imprisonment within the Tree of Woe. This truth intertwines his personal stakes with the battle against the Tree’s devastation. After neutralizing the Tree, the Arc Ruler erases public memory of his contributions, crediting the Seven Shadows instead, allowing Hiiro and his allies to reclaim ordinary lives.

His bonds with figures like Luca and Light Tenryu reflect his evolution from novice to leader, balancing duty and sacrifice. Transitioning from a determined player to a pivotal force against global collapse, his journey epitomizes adaptability and resilience, mirrored in his shifting strategies yet anchored by an unwavering will to safeguard humanity.