There's a Mutant Fungus Among Us in Matango (1963)
Given how much Ishiro Honda has contributed to the horror film subgenre of kaiju flicks, it's easy to forget some of the other top-notch horror films that he made throughout his career. Case in point: Matango, Honda's surreal mood piece from 1963 that was loosely adapted from the short story "The Voice in the Night" by William Hope Hodgson.
Matango tells the story of the crew of a luxury yacht, which consists of a wealthy Japanese businessman, five of his friends, and a hired skipper. After a violent storm interrupts their leisurely afternoon excursion at sea, the yacht's crew becomes stranded on an uncharted island. Their search for food and shelter leads them to the remains of an abandoned schooner that's covered by an odd and possibly edible fungus. As the crew's cohesion as a group begins to deteriorate, they learn more about the connection between the missing schooner crew and the fungus and that they too might share the same ghastly fate.
The outwardly simple plot of Matango allows for comparisons to subsequent horror films such as The Flesh Eaters, Planet of the Vampires and Night of the Living Dead. It also doesn't help that the American release of Matango renamed it with an amusingly hokey title: Attack of the Mushroom People. Yes, there are disfigured, mushroom-like people who attack during the course of the movie, but Honda directed this film not as a cheapjack creature feature but as a character-driven commentary about the decadent upper class that rose to power in Japan in the shadow of the Atomic Age.
A "mushroom people" mask from Matango.
Matango is essentially a story about the corrosive nature of addiction, with the fungus and the deleterious effects it has on those who consume it being the symbols of addition. In that regard, the most obvious source of influence for Matango and the story upon which it is based is the lotus-eaters segment in Homer's The Odyssey--namely, the idea of how an addiction can cause people to lose touch with who and what they really are. Where Matango differs from that concept and Hodgson's original story is in Honda's suggestion that the yacht crew were already addicted to wealth and the seemingly unlimited pleasures that it provides long before they arrived on the island.
The crew's separation from affluence causes their social hierarchy to dissolve into chaotic self-interest; the crew's eventual fungal addiction merely externalizes what was already present within their hearts and minds. Honda's effective usage of dreamlike visions and gaudy flashbacks throughout the second half of the film emphasizes how the crew members are not only losing touch with reality, but that their grasp on reality was already distorted due to their privileged lifestyles.
The fungus also represents the destructive nature of atomic warfare, since the fungus' origin in the movie is attributed to genetic mutation caused by radiation. Such a connection adds a grim sense of urgency to the movie's moral lesson, that ignoring the dangers of atomic technology in favor of unbridled self-indulgence will ultimately destroy all of humanity. (Thematically speaking, the fate of the wrecked schooner's crew is very similar to the crew of the abandoned fishing boat in one of Honda's previous Atomic Age-influenced films, The H-Man.)