Koizumi passed away last Sunday, said The Hollywood Reporter.
Making his film debut in 1951, the actor appeared in a string of monster films, including three in 1964 alone, "Mothra vs Godzilla", "Ghidorah, "the Three-Headed Monster" and "Dogara, the Space Monster".
In 1955's "Godzilla Raids Again", Koizumi appeared as a pilot, who discovers Godzilla battling another monster on a remote island.
The film was put into production by the film company, Toho, to cash in on the box office success of the first "Godzilla" film the year before.
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Shortly after, he signed for Toho: in those days actors were usually contracted to work for a single studio.
Koizumi also acted in numerous non-monster productions, including the "47 Samurai" in 1962, alongside the legendary Toshiro Mifune.
The film was one of the many versions of the true story that was the basis of the Keanu Reeves flop, 47 Ronin, in 2013.
During the 1970s, he became the presenter of Fuji TV's popular Quiz Grand Prix, though that did not stop him returning to the big screen for 1974's "Godzilla vs Mechagodzilla".