The series follows Taisuke Kanou, a teenage student in Japan who lives a normal life with his sister Yoko Kanou. The story begins when a dark being from space senses life on Earth, the sky becomes dark and mass suicides occur worldwide. It is learned that the being, Akuro, is composed of souls who were granted immortality and who wanted to die but could not do so without a body. These beings separated from each other and entered the bodies of humans in order to commit suicide. The main characters of the story are possessed humans who resisted the temptation, known as "Comrades."
When Taisuke's friend, Yuichi Hirose, discovers his powers he kidnaps fellow friend Megumi Ochai and heads north to the heart of Akuro. Taisuke, obtaining his own powers, follows in an attempt to bring Hirose and Megumi back home. On his adventures, he is accompanied by fellow comrades Yuta Takizawa and Nami Kusonoki. He tracks down Hirose to a lake where the latter absorbs Akuro's heart. Taisuke defeats Hirose by triggering a volcanic eruption, which apparently kills them both and destroys the heart.
Two years later Yuta and Nami learn from Aoi Tezuka and Jun Tezuka that Taisuke is alive. They meet Taisuke, who is revealed to have amnesia, though he soon regains his memories. They learn from Yukie Tezuka that the army has the dormant Hirose, along with the heart of Akuro, and that they must set out to destroy it. After several attempts to destroy the heart, Hirose awakens and flees from the military base. Deducing Hirose's return to Japan, Taisuke and his friends prepare for the upcoming battle.