In a contemporary setting, a wave of 'Despair People' lacking ego due to surging negative emotions plagues society. These afflicted individuals play host to parasitic monsters born of their bleak thoughts, causing societal chaos. Amida, a high school student, is unexpectedly chosen as a hero by the enigmatic extraterrestrial being Infinity X. Endowed with the unique power to venture into the depths of human psyches, she combats these monsters with her 'power of imagination.' Yet, as she battles, she uncovers a troubling truth - with each victory, she absorbs fragments of the host's memories. Amidst this moral dilemma, her closest friend Kirari falls victim to the despairing affliction...