The first episode of The Return of Ultraman, the first entry in the Ultra Series following Eiji Tsuburaya's death, airs on April 21, 1971 in Japan.
The first episode of Mirrorman airs on December 5, 1971 in Japan.
In the Kaiju Multiverse
Godzilla emerges to battle the smog monster Hedorah, a giant space creature that feeds on pollution. With the help of two giant electrodes, Godzilla triumphs, but not until he suffers greatly from Hedorah's vast array of abilities. (Godzilla vs. Hedorah)