Ultraman’s defeat seems to have come as a bolt from the blue even for the SSSP cast members.
It is likely they learnt the end of the series for the first time when they looked at the name of Zetton associated with the last character of the alphabet and Fuji’s line ‘Goodbye!’ in the script.
It seems the possibility to extend the series with the high viewing rates of all time to four seasons was studied, but it was abandoned because of the tight shooting schedule eventually.
I wish I could have seen one more season of Ultraman.
Thus Ultraman came to an end with 39 episodes, and, after half a year interval during which Toei’s Captain Ultra was aired, Ultraseven got started.
It may be noteworthy that Episode 38 and 39 of Ultraman seem to show the transition of the series.
Episode 38 was about a battle with monsters on another planet, which was a full-scale space action story in the series of Ultraman.
This style of space action is said to have been plotted during the early stage of preparation for the following Ultraseven while it was prepared under the provisional title Ultra Garrison.
Incidentally Ultra Garrison was supposed to be a product featuring the Ultra Garrison with no superhero like Ultraman.
Episode 39 got the style of an invading alien and a monster controlled by him established, which you can see in Ultraseven. (The scene with the VTOLs chasing the alien’s spacecraft in valleys is so similar to that of Episode 1 of Ultraseven.)
These episodes could be deemed to herald the coming of Ultraseven after Toei’s space action drama Captain Ultra.