Attack Of The Monsters (1969)

Starring Nobuhiro Kajima, Miyuki Akiyama, Christopher Murphy, Yuko Hamada, Eiji Funakoshi
Directed by Noriaki Yuasa
(actor & director credits courtesy IMDB.com)

Two young boys enter a flying saucer that's landed on Earth, and are transported to another planet, whose residents have sinister plans for them, but Gamera comes to the rescue.

Gamera the flying turtle monster returns in this especially kid-centric installment in the series, also known as Gamera Vs. Guiron, with one of the boys played by Caucasian actor Murphy, perhaps with an eye on increasing grosses for this one in the U.S. film market.  The film also returns prior Gamera foe Gaos, in a different color to avoid explaining his resurrection, but Gamera's primary foe this time is Guiron, whose head is shaped like a giant sharp edged knife, and is able to eject throwing stars from its body.  However the bulk of the film is focused on the boys, who easily trust the female aliens they meet, before discovering the beautiful ladies have ulterior motives.  I thought this was a refreshing change from some of the more monster-battle heavy entries in Gamera history, and although the special effects are not among the best in the series, there's some interesting ones on display.