See my thread on summiting a local 11,930 ft. mountain. My buddy and I camped within 3 miles of the summit the night before. In the morning I ditched (cached) my pack out of sight and carried a small daypack/stuffsack REI Flash because I knew my main pack was only 3 miles from the summit.

That said I DID carry a survival kit W. a space blanket, 2 liters of water, gloves, food, stocking cap and GTX parka (which I had to wear near the summit).

OK, it was a very short summit dash in the morning of a summer day in southern Nevada. Even so temps were 40s F. with 25 - 30 mph. winds. For a REAL summit attempt, say on a fourteener in the Sierra Nevada or Colorado I'd take my 2,500 cu. in. winter backcountry skiing daypack with more clothes, food and shelter gear. It's all in understanding the "Worst Case Scenario" and preparing for it.

Clearly Japanese hike leaders did not exercise due diligence in checking participants' gear before starting a climb. They were at least as much at fault as the climbers, whether they were paid professionals or experienced volunteers.

Eric