Dying of old age, Kaibara organizes the creation of the biologically fused boomers. His intent was to transfer his personality into one of them and continue living in a new body that couldn't age or die. Liam Fletcher was a prototype made from a body of a human who already existed and as such, imperfect. Hans Kleif was the finished version of the new boomer, made by scratch from Genom. Yuki Satomi was one of the people that worked on the project.
A second Hans Kleif was later made by Genom, and Kaibara's personality was successfully transferred into it. His new body is considered the perfected version of Hans Kleif, but he was killed with Hans when Kenji shot both of them to prevent Kaibara from escaping.