About 13,500 Japanese civilians survived the battle; 1/2 of them under 16 years old. The number of deaths during the battle isn't well known, since Japan made an attempt to bring about 3000-5000 of the civilians back to Japan (with about 1700 deaths when Amerika Maru was sunk by a US submarine after leaving Saipan).

After the battle, all of the civilians on Saipan were interned in a camp at the south of the island: Camp Susupe. Initially, there were about 18,000 internees: approximately 13,500 Japanese civilians, 3,000 indigenous people (Chamorro and Carolinians), and 1,500 Korean civilian labourers who had been conscripted to work for the Japanese military. The Koreans would have been predominantly adult men, and the other groups men, women, and children. The camp was divided into 3 separate areas, based on these ethnic groups. Many (most?) of the "Japanese" civilians were actually Okinawan, but the US did not yet differentiate between Japanese and Okinawans.

While the Chamorro and Carolinians were interned, they were given better housing, and worked as camp guards (with some gaining a reputation for brutality in this role).

Japanese internees, including women, were used for labour, in principle voluntary, but in practice there was enough compulsion that "forced" is a fair description. A Japanese police force was used to maintain order insider the Japanese camp (with Chamorro and Carolinians guards controlling the perimeter).

In the first few months of the US occupation of Saipan, about 1,000 civilians died per month in the camp. As housing, food, and medical care improved, the death rate fell. Unfortunately, I don't know how many survived to be repatriated in late 1945 and 1946. (If you do find a number, note that there were about 500 Japanese POWs and 500 Korean POWs on Saipan in addition to the civilians.) The Japanese civilians and POWs were repatriated to Japan, and the Koreans to Korea, with the exception of some Japanese settlers who had married indigenous people (and who were interned with the indigenous civilians rather than the Japanese civilians).

Further reading:

Life in the camp, in great detail:

• Norman Meller, Saipan's Camp Susupe, Occasional Paper 42, Center for Pacific Islands Studies, University of Hawai'i at Manoa, 1999. https://core.ac.uk/download/pdf/5104027.pdf

Briefer:

• Beatrice Trefalt (2009), "After the Battle for Saipan: the Internment of Japanese Civilians at Camp Susupe, 1944-1946", Japanese Studies 29:3, 337-352, http://dx.doi.org/10.1080/10371390903298037 https://www.researchgate.net/publication/233377396