Mary, a shy anime girl, is thrust into a world of sinful pleasure when her brother challenges her to a game of 'Go'. The rules are simple: Mary must move her pieces while her brother pleasures her, stopping only when she surrenders. As the game progresses, Mary's moans echo through the room, her body writhing in ecstasy as her brother's skilled hands and tongue bring her to the brink of orgasm. But Mary won't give in so easily, determined to outlast her brother in this erotic battle of wits.