It is the year 2020, and a nation is under constant threat from the "Others," terrifying monsters that mysteriously enter the atmosphere and feed on human brains. In a moment of hope, psionics, a hormone that grants certain people extrasensory abilities to combat the Others, is discovered in humans. The nation's founder creates the Other Suppression Force (OSF), also known as the Scarlet Guardians, to fend off these creatures and save humanity. Young individuals with psionics undergo intense training to join this elite group. After enduring rigorous training, exceptional recruits are prepared for their induction ceremony to become Scarlet Guardians. Yuito Sumeragi, the son of the nation's founder and a determined individual, is among them. As a child, he was saved by a woman in the OSF, and he is eager to join the organization to repay his debt and protect humanity. However, when he meets his new comrades, he is troubled by the fact that the woman who saved him bears a striking resemblance to one of his teammates. Yuito is unaware that a dangerous conspiracy is brewing and has the potential to devastate the entire country. Despite his concerns about his savior and teammate's uncanny resemblance, Yuito soon realizes that this is only the beginning of his problems.