Scarlet Nexus

In 2020, a strange phenomenon known as the "Others" began to appear; these creatures would descend from the sky and feed on human brains. Shortly afterwards, a hormone allowing certain people to have extrasensory powers was discovered, which could be used to fight the Others. In response, the nation's founder created the Other Suppression Force (OSF), also known as the Scarlet Guardians, to combat the monsters and save humanity.

To join the OSF, young people with psionics underwent rigorous training and an induction ceremony was held to recognize the exceptional recruits. One of the chosen was Yuito Sumeragi, the son of the nation's founder. He was saved by a woman in the OSF when he was five, and joined to repay the debt. However, Yuito was unaware of a sinister conspiracy that could endanger the entire country.