TOKYO, April 22 — The young Japanese civilians taken hostage in Iraq returned home this week, not to the warmth of a yellow-ribbon embrace but to a disapproving nation's cold stare. Three of them, including a woman who helped street children on the streets of Baghdad, appeared on television two weeks ago as their knife-brandishing kidnappers threatened to slit their throats. A few days after their release, they landed here on Sunday, in the eye of a peculiarly Japanese storm. "You got what you deserve!" read one hand-written sign at the airport where they landed. "You are Japan's shame," another...