As a part of Higurashi no Naku Koro ni Hō, the Une virus is a lethal virus that depletes living beings of their nourishment. Une is the leader of an alien strain of parasitic microorganisms that recently arrived on Earth. The virus is as virulent as η-173, and Une wants to infect humans, which motivates Tamurahime no Mikoto to spread η-173 to prevent the lethal Une infection.

After Une infects humans with the virus, the infection soon spreads into a pandemic. After seven weeks, the human population decreases to 20 percent. When there are no more humans left to infect, Une plans to move on to another inhabited planet and spread her seeds of destruction there. However, Une could not infect the remaining population as her plans were halted by Furude Rika who committed suicide which reversed time to a point before Outbreak, allowing the club members to restrain Une and the other two gods before she could infect anyone with her virus.