The patriarch’s fear is of nuclear annihilation, and in the end it annihilates him by annihilating his sanity.
The patriarch intends to save all his blood family, both marital and extramarital, and move it from what may become a destroyed Japan to the relative safety of Brazil. The members of the family want only to keep what they have, and what they will gain by his death or a legal declaration of mental incompetence. The family court sides with the family, and puts aside all aspects of atomic annihilation, except to conclude that the patriarch is indeed in the wrong and is incompetent.
The familial objection is to his fear, not to its source.
The film was made three years after the end of the American occupation of Japan. Japan is the only country to have been attacked with nuclear weapons. The Korean War had concluded in 1953, and was a proxy war for nuclear superpowers. Hydrogen bomb testing in the Pacific (since 1954) caused Japan to reduce its limit its consumption of fish and seafood. In 1955, American jet planes continued to patrol the air over Tokyo.
Radioactivity incinerates. It does not arise solely from nuclear weapons. The waste generated by coal-fired power plants is more radioactive than nuclear plants. A byproduct of burnt coal is fly ash, which deposits into the environemnt one hundred times more radiation than a nuclear plant of equivalent production of electricity.
The metaphor of ash is introduced early in the film within the metaphor of the foundry. The foundry is the family business. Foundries use coke, a manmade substance. Waste water from coking is lethally toxic and carcinogenic. The higher the ash content the less the quality of the coke for blast furnace operation. 8% is the preferred level; in the film the coke delivered to the foundry has 12% ash, which is why the owner, the patriarch, pays less than asked.
Foundries make metal casings, such as those for bombs.
In the end, the patriarch immolates his foundry not only to convince his family of his fear, but also, more deeply, to attempt to extricate his fear from the source of the ashes by destroying the means of their production.
Twenty-three American nuclear detonations occurred on Bikini atoll between 1946 and 1958, on the reef, on the ocean, in the atmosphere, and underwater. The 1954 series of thermonuclear hydrogen bombs that were of a power 1,000 times greater than the bombs that demolished Hiroshima and Nagasaki. Within two hours of detonation of a test in March, 1954, the crew of a Japanese fishing boat were contaminated by irradiated fallout and ash. All soon suffered acute radiation poisoning. The Hungarian-American physicist, Edward Teller, participated in the Manhattan Project, and became known as the “father of the hydrogen bomb.” His comment on media reportage and commentary on the death of one of the contaminated Japanese fishermen was: “It’s unreasonable to make such a big deal over the death of a fisherman.”
So, what exactly is madness? The atoll was rendered uninhabitable. Chernobyl, a different kind of nuclear manifestation with similar consequences, is more recent. Parts of New Mexico and Nevada have been rendered lifeless desert. The list stays permanently incomplete as it grows. We are blinded by light, and the skin of our existence is flayed from us.