Not long after the appearance of the gate, a group went in to investigate the gate. Among the group only one man survived. Tahara now spends his time in his office taking care of the flower he found in the gate. But things are about to change as a group targets him for his research on contractors and the gate. Can Hei and the others get the information first?

Gai and Kiko get hired by a widow and are asked to find the widow's lost black cat. While trying to find the cat, they meet Hei, who is looking for the Contractor that is killing employers from that same company. As both Gai and Kiko continue to look, Gai comes across the skeleton of a woman who has been dead for a while.

After Hei and Misaki barely escape from Alice, Hei goes his separate way after Misaki and Saitou find each other. After Hei steals the crystal hidden within the stone flower garden, he runs into Wei and loses the crystal in the process. Wei finally meets up with Misaki and Saitou, who have found Alice. After Wei kills his partner, Alice, he moves in on Misaki and Hei.

Kastenin, Gai, and Kiko take Yin back to her home town, meanwhile Hei is given the order to kill Yin and is given her location. Getting to Yin is not going to be that easy since th contractors from before are still after Yin and have their own method to finding her. The race is on once more, but this time Hei must make the choice on whether or not to kill Yin. Will he kill her or will the option be taken from him?

Hei is sent to infiltrate a religious organization and kill the Prophet, Alma. He is aided by an insider, another Contractor by the name of Shihoko whom Huang appears to know. Amagiri and Alma appear to be in cahoots with Alma providing him with dolls. A well-meant mistake on Huang's part leads to Shihoko's capture.

Mayu Otsuka works at the 4th Foreign Affairs Department in the Japanese National Police Agency as a liaison officer with the National Astronomical Observatory of Japan. She wrote a story about a masked man that supposedly seemed to be a dream, but she isn't sure. Hei and his comrades got themselves a new task and are looking for a numeric password with a sample. A contractor took it from the Gate and buried it under a blossom tree. As events unfold, Mayu seems to fall in love with Hei, while Saitou struggles to confess his feelings for Kirihara.

Suo and July find themselves in a dangerous situation thanks to a double-crossing supposed ally. Later, when the young pair is abducted by an especially sinister Contractor, BK-201 must spring into action.