Zero-gou

"It's man's creation, a human sacfifice, to oppose the force of the Nanagou. It is our ultimate weapon, Zero-gou."

- Murasaki Iyo, Chapter 93

The Zero-gou (零郷, Zero-gō) is an artificial Nanagou designed by Usuzumi Iyo, developed by the Senate, located in the lowest floor of their basement, B108. It currently hosts all member of the Lost Generation within it.

The Zero-gou is nearly identical in height, weight and diameter to the Nanagou. Just as the Nanagou are marked with their respecitve number, the Zero-gou is marked with "零". At the bottom of the Zero-gou are thirty-six doors equally spaced around its perimeter, each labeled with the names of members of the Lost Generation.

History
The Zero-gou was designed by Usuzumi Iyo as a means of negating the merging of worlds caused by the Nanagou without using the Hiizumi Clan's Stepping Stone Ritual. Usuzumi struggled with the Zero-gou completion until Shidare Morioka, Uzu Kibune and Lucy Rang Miraclouse joined him at the Senate.

Shidare conducted the first trial test of the Zero-gou using Lucy as the test subject. Though Lucy told Shidare not stop the experiment until he believed it was time but was stopped by Usuzumi who initiated the emergency eject. Lucy returned having aged dramatically in the short time she was in the Zero-gou. With the data gathered from he experiment, the Zero-gou was able to be completed and Shidare developed the operation plan.

Usuzumi and Makiharu attempted to enter the Zero-gou in place of their sons who had volunteered but were stopped and incapacitated by them. Shidare had Makiharu's son enter first and over the next three years the selected subjects would be chosen and enter the Zero-gou within a specified order.

After the thirty-six subjects were placed within, Usuzumi confirmed the effects of the Zero-gou to be functioning with no effect on the yōkai of the world and begun conducting research to extract the Lost Generation from the Zero-gou. Usuzumi created a key which would maximize the output of the Zero-gou, in case one would ever attempt to accelerate the merging of worlds. Machi had Yūhi Shinatsuhiko tranform the key into a cylinder that would require tuning to return to its orignal form and returned it to Usuzumi. This was to ensure that if the key was to ever be used it would require both the Iyo and Hiizumi Clan to cooperate.

Function
The Zero-gou functions as the Senate's ultimate weapon to oppose the merging of worlds brought upon by the Nanagou. The Zero-gou works by the life force of of the thirty-six members of the Lost Generation, located within the thirty-six doors of its perimeter. Each person within the Zero-gou was selected based on the quality of the life energy and entered within the allocated ports in a specified order to maintain balance. If the balance of the Zero-gou were to break it would malfunction and lose control.

A key exists which can be used to maximize the output of the Zero-gou, though resulting in the deaths of those within it. Yūhi Shinatsuhiko transformed the key into a cylinder, which required tuning to return to its original form, in order to ensure that if it was ever used, had the cooperation of both the Iyo and Hiizumi Clan.