This is the only film in the original series to not feature a child as the main human character.
The film was initially meant to be more adult-oriented, with the native island dancers appearing topless. While the movie was relatively serious and had some more adult moments such as intense fights, in the end the movie was released with child audiences in mind.
The first draft of the script didn't have any references to the first movie.
The original idea for the film involved ice-based aliens invading Earth and oppressing humanity. Another idea the studio considered involved an ice giant from Scandinavian folklore. Eventually, the ice concept was carried over into Barugon's freezing ability.
This film is noticeable in the Showa Gamera series due to its lack of a child protagonist and a more serious atmosphere. Daiei took notice that the children were restless during the human drama and playing in the rows in the non-monster scenes. For the subsequent film Daiei would add a child protagonists and increase the kaiju mayhem to appeal to the short attention spans of fans.