"Kaijus are terrorizing humanity in the year 1954. However, scientists make a discovery that can change everything."
In this scenario, Kaijus are discovered to be simply females in heat going berserk because they can't find a mate.
So scientists turn (You) into a giant 'flesh mecha', Attack on Titan style, so you can wrestle-fuck them until they're satisfied.
You are:
The Kaiju's Layer