In 1968 Daiei produced their fourth annual Gamera feature. While the third film, Gamera vs Gyaos, had been a commercial success, other films released by Daiei had not been so lucky. While the studio was keen to profit from a fourth Gamera – and invited back Noriaki Yuasa to direct it – their finances were in dire straits. Both the shooting schedule and production budget were cut to the bone.

Thus the biggest surprise of Gamera vs Viras is just how entertaining a film it is. It follows Masao and Jim: two boy scouts who abscond with a mini-submarine, only to encounter the giant alien turtle Gamera and get kidnapped by a mysterious race of aliens intent on invading the planet Earth. It pushes the franchise even further towards being a series for children: it is children who are the narrative focus, children who encounter the Viras, and children who – with Gamera’s assistance – save the day.

There a visible budget shortfalls throughout the film, all of which are forgivable because Niisan Takahashi’s screenplay has been written with such integrity and surprising inventiveness. For the most part Gamera is not fighting another giant monster but rather a strange alien spacecraft. Much of the action takes place inside that alien ship, where Masao and Jim are held hostage. It is a different style of science fiction adventure that featured in the first three Gamera films, and that is a refreshing change that makes the fourth particularly enjoyable. The design work is bold and appealing, although when a giant monster does turn up during the climax it is far and away the goofiest-looking that the series has had.

The budget problems led Yuasa to use archival footage for much of the Gamera scenes, liberally taking scenes from the original Gamera the Giant Monster (1965) and tinting them purple. It is disappointing, given how much of the appeal in these old kaiju films lies in the rubber-suit sequences, but it does fit well enough into the narrative to work. Scenes onboard the Viras ship are a decent consolation, and manage more often than that to feel genuinely creepy. The workers living aboard the ship certainly look human on the outside, but their strange glowing eyes tell a different story.

Toro Takatsuka and Carl Craig play the young protagonists very amiably. It is particularly impressive how well Craig acquits himself. A contractual obligation for American co-funding required an American boy who could speak Japanese, and Craig – a non-actor whose father lived in Japan as part of the US armed forces – does a superb job in what is his first-ever acting gig. And he does it in Japanese. By this stage of the series the film’s adult cast essentially exist solely to frame the children’s adventure, but it is notable to see Daiei stalwart Kojiro Hongo in his third Gamera role in as many films.

Gamera vs Viras is cheap as all hell, but Yuasa has managed to direct a film that is modestly-made but neatly delivered. As a showcase for Gamera itself, it is sadly the weakest of the series so far. As a breezy children’s adventure with a healthy dose of 1960s kitsch, it is a charming little confection.