In the enigmatic Lightless Realm, a band of youngsters forges unbreakable bonds before being whisked back to their reality. Years later, these comrades reunite to combat 'Admonitions,' monstrous beings emerging from that very void, utilizing mechanized warriors called 'Vess.' Despite their valiant struggles, the relentless spread of the Lightless Realm persists. A grave twist unfolds as a new adversary, the lethal 'Corpse,' emerges with a haunting melody rumored to claim lives within nine days of hearing it. The group falls victim to the 'Corpse Song,' unraveling their unity as personal dilemmas threaten to upend humanity's destiny.