Prime Minister Shinzo Abe says he believes the government will not disclose official documents on how the new era name "Reiwa" was selected for about 30 years.
Abe said this on NHK's "News Watch 9" TV program on Monday night.
He said he believes a period of about 30 years will basically be necessary to protect the reputation of those in charge of coming up with the selected name and other candidates.
Abe also revealed that the first time he saw the proposed name "Reiwa" was in March.
He said he saw it in a report from Chief Cabinet Secretary Yoshihide Suga, who had sorted out proposals from scholars and other experts. Abe added that it sounded vivid when he was briefed on it.
The new name was taken from Manyoshu, the oldest existing anthology of Japanese poetry.
Abe said most of the members involved in the selection process had called for the new era name to be chosen from classical Japanese literature.