Aliens have invaded the Earth, and people are forced to flee to a giant bunker underground. SUM1 is a loyal soldier who was sent to the surface to rescue the survivors and report the situation every day. His mission is to guard the human self-defense zone to prevent aliens from approaching, but this daily routine task gradually becomes his nightmare. Terrifying sounds echo in the woods; the base is frequently attacked every day; the power supply in the tower fails; and the repairman is slow to show up. His boss never told him about his predecessor. Loneliness and paranoia slowly erode his sanity. Are aliens really lurking in the forest? Or has SUM1 been tortured to insanity?