The Age of Assassins (1967)

A nerdy young college instructor named Shinji Kikyo returns home one day to find himself the target of a mad assassin. Surviving somewhat miraculously, he fends off other assassins and with the help of reporter Keiko Tsurumaki and car mechanic Bill Otomo, eventually discovering that a "population control" association is really an assassination squad led by Shogo Mizorogi, who has been training patients of a mental asylum to become killers.