Arakura Arato is a high school student whose life philosophy is crisis avoidance. His constant vigilance has manifested as an invisible barrier, an EMO ability—supernatural powers born from strong emotions. His quiet, low-key existence shatters when he is suddenly attacked by Konomi Kirara, a woman with the ability to rot matter. Konomi reveals that she is an officer of CES, the Counter EMO Squad, and that Arato is an EMO user. She explains that EMO abilities are rooted in the user's core emotions, as mapped on psychologist Robert Plutchik's Wheel of Emotions.

Forced to defend himself with only a defensive barrier, Arato manages to outwit Konomi in their first encounter, but this draws him into a hidden conflict between EMO users. He learns that his beloved younger sister, Aira, is also an EMO user and has been kidnapped by a criminal organization known as the Masked. To find her, Arato agrees to cooperate with CES. He is assigned to a team of eccentric colleagues, including the justice-driven Konomi, and begins investigating the Masked's activities.

The narrative follows Arato as he battles a variety of EMO users—enemies who can reverse time, shatter objects, manipulate probability, and more. Each power corresponds to a specific emotion, turning fights into tactical puzzles where Arato must exploit his versatile but purely defensive barrier. As he grows closer to his CES teammates, he struggles with the revelation that Aira has become a willing member of the Masked, her memory erased after a clash. Arato's own ability suddenly vanishes during a series of escalating incidents, leaving him vulnerable. The Masked launch a direct assault on CES headquarters, where a user of "fate" overwhelms the team with probability manipulation. Utterly defeated and rejected by his memory-wiped sister, Arato sinks into despair. However, bolstered by his comrades, he resolves to rise again and launches a counterattack to reclaim Aira and stop the Masked's plans. The story is a psychological battle manga where emotions are weapons and the line between protector and threat constantly blurs.