Construction of Mukyudo Cave by Miyamura School Students (1943–1945)

Sasebo, in Nagasaki Prefecture, was the seat of one of the Imperial Navy's four naval districts, with a naval port and arsenal, and was regarded as a likely target for air attack late in the war. Miyamura National School (now Miya Elementary School) lay in a rural district on the city's outskirts, but Principal Ikeda Chiaki nonetheless conceived and directed the construction of Mukyudo as American bombing intensified: a shelter cut into the hillside behind the school, large enough for all its pupils and able to serve as a classroom during raids. The name Mukyu ('without end') expressed the wish that the children's lives and futures should not be cut short.

Work began on 29 August 1943, with teachers leading pupils in morning and afternoon shifts; no explosives were used. Older boys, from the fourth grade up and especially those of the higher course, excavated with pickaxes and hoes, older girls smoothed the walls with chisels, and younger children carried debris out of the cave. The cave was carved from soft volcanic tufa rock, making child labor feasible though still arduous. Work continued daily for nearly two years until Japan's surrender on August 15, 1945.

The finished shelter has a main chamber about 5 metres wide and 19-20 metres deep and a secondary chamber about 3 metres wide and 15 metres deep. It included a classroom with stone lectern, a kitchen with two cooking stoves, toilets, food storage, an Imperial portrait room, ventilation openings, a manual air pump, and an emergency stairwell; the lectern and the arched ceiling were cut directly from the rock. Local Sasebo accounts give its capacity as about 600 pupils, while Japanese Wikipedia gives 500. Central Sasebo was heavily bombed at the end of June 1945, but outlying Miyamura was not directly attacked.

The shelter survived intact after the war. It was opened to the general public in 2002 to mark the centenary of Sasebo's incorporation as a city, with local volunteers acting as guides, and is now one of Sasebo's best-known war sites and a place of peace education on the wartime mobilisation of schoolchildren and life under the threat of air raids.