The night is cool, Park Avenue South is busy with traffic. Machiko walks. Few people move along the broad sidewalks at this hour, for although the district is well-patrolled by NYPD Inc. and others, and no part of Manhattan ever truly seems to sleep, the district is not without problems. Those few who are out and about stay in groups and move briskly. They keep to the brilliant lights of the avenues, shunning the darker confines of cross-streets.