From the introduction:
In the 17th year of the Showa Period, at a village in the mountains of H Province, six mummified bodies were excavated.The bodies were about 60 cm in length and were placed in wooden crates sealed with shimenawa ropes. Each body seemed to take the shape of a curled-up newborn.
During the second world war, the Japanese Army Research Institute took this discovery into consideration. Thanks to surplus funding from the government, they began research on using human bodies as weapons. However, the whole establishment vanished, along with their data and the original mummies, due to the post-war chaos. The name of this establishment is “SAI”.
In the modern day, SAI is alive in well, and is implanting cells from the mummies to create monsters called Amalgams. Though only 1/10000 survive.