Frankenstein Conquers the World
フランケンシュタイン対地底怪獣 (original)
During WWII, Germans obtain the immortal heart of Frankenstein's monster and transport it to Japan to prevent it being seized by the Allies. Kept in a Hiroshima laboratory, it is seeming lost when the United States destroys the city with the atomic bomb. Years later a wild boy is discovered wandering the streets of the city alone, born of the immortal heart.
Starring Tadao Takashima, Nick Adams, Kumi Mizuno, Yoshio Tsuchiya, Jun Tazaki, Susumu Fujita, Takashi Shimura, Nobuo Nakamura, Kenji Sahara, Yoshifumi Tajima
It's a science-fiction and horror movie, and has a rating of 5.5 out of 10 from Imdb which is fairly okay for this kind of movie.
Watch it here
Not found streaming from Finland.