Centuries ago, the Hypnos Comet hit Earth, causing global storms but leaving no trace. It led to the emergence of new humans, "Rovers," who project others into a mental dimension, causing madness, while rare "Fantasts" can adapt and use mental energy. The comet also brought invisible creatures, "Xulthrok," randomly killing and spreading fear. To address these threats, the Spirit Investigation Association (S.I.A.) was formed to study the comet's effects, along with the Neutralization institution.