The only disbelief I have is where Koko would find 200,000 odd tons of steel and armour to produce these four monsters?
Indigenous deposits on the islands of Suiko, Jimmu, Tenji, Fujiwara, Hyoto and Shinjima, first discovered by Portugese surveys in the early 17th century and regularly exploited since the 1880s. There is enough to even allow some exports to support Japanese naval constructions until 1945.