TOKYO — From the prime minister to ordinary people, Japanese were shocked Sunday at a video purportedly showing one of two Japanese hostages of the extremist Islamic State group had been killed. With attention focused on efforts to save the other hostage, some also criticized Prime Minister Shinzo Abe’s drive for a more assertive Japan as responsible for the hostage crisis. A somber Abe appeared on public broadcaster NHK early Sunday demanding the militants release 47-year-old journalist Kenji Goto unharmed.