The Mirror Twins Evil series referred to a series of light novels developed by Hololive. There were three books in total, namely, The Disappearance of the Mirror Twins, The Demons of the Mirror Twins, and The Disappearance of the Mirror Twins (Part 1). The Three Tragedies referred to the three famous songs created by Mirror Sound Bell: "The Disappearance of Mirror Sound Bell"(Disappearance of Mirror Sound Bell),"Demon's Eye"(Demon's Eye), and "Song of Tianxiang"(Tianxiang Gifts). These three songs became one of the representative works of Mirror Sound Twin Evil Series. In addition,"Song of Tianxiang" was the ending song of "The Disappearance of the Mirror Bell (Part One)" and "The Eye of the Devil" was the opening song of "The Disappearance of the Mirror Bell (Part Two)".