Sekai Oni's storyline follows Shinonome Azuma, a young girl who lives with her uncle's family after misplacing her parents. Despite her new caretakers, Azuma endures harsh treatment and abuse, which results in her developing a rare condition called Alice in Mirrorland. This affliction causes her to see her illusions reflected in mirrors, water, and other reflective surfaces. However, when these visions start to cross over into reality, the line between fantasy and truth crumbles, leading Azuma to the entrance of a world beyond the looking glass - a place known as Wonderland.
