Kyodo News agency and other Japanese media said the former detainee later returned to Japan.
Motegi said another Japanese national who was arrested earlier this year is still in custody.
Motegi said the release came after his repeated demands to Iranian Foreign Minister Abbas Araghchi and that he is “working to win an early release” of the other detainee while communicating with his family and other concerned parties.
The Committee to Protect Journalists has named the person detained in Iran in January as a journalist at Japan’s public broadcaster NHK. The CPJ said the NHK journalist was arrested Jan. 20 by the Islamic Revolutionary Guard Corps and was transferred Feb. 23 to Evin Prison, quoting unidentified sources citing fear of persecution.
Motegi did not identify either of the people detained but said the released Japanese national was detained in 2025.
The Foreign Ministry said earlier this month the detainees were safe and in good health, but only acknowledged that one was detained last year and the other one in January.
The ministry gave no further details and did not say whether the two cases were related.