Suigin Riku is a cash-strapped high school student who works multiple part-time jobs to pay for tuition. He's out of his element when he enrolls at Shinryou Private Academy, an opulent institution for the wealthy. While attempting to rescue his cat from drowning, Suigin, who can't swim, plunges into a deep pool. That's where he meets Rei Riku, the alluring daughter of a game developer, who captures his heart. Suigin's affections are complicated when he connects with another girl via Dungeon Century, an online RPG he adores. However, the game is abruptly shuttered, cutting their virtual romance short. The next day, Suigin is stunned when he realizes the girl from the game is Rei. She hands him Grave Buster, a new video game, informing him that he must conquer it to save her life. In Gin no Guardian, Suigin immerses himself in Grave Buster, unlocks its secrets, and sets out on an epic quest to rescue the love of his life.