The 2019 Japanese imperial transition occurred on 30 April 2019 when the then 85-year-old Emperor Akihito of Japan abdicated from the Chrysanthemum Throne after reigning for 30 years, becoming the first Emperor of Japan to do so since 1817. The Enthronement Ceremony for Emperor Naruhito took place in Tokyo on 22 October 2019, marking the end of the transition period.
Stamps:
Enthronement of Emperor Naruhito (full set) - Issued: 18-10-2019
Many thanks to Mitsuhiko!