Among a sea of men in black tailcoats, there was one guest, dressed in a light silk kimono, who easily stood out during the rituals-steeped accession ceremony for Japan’s new emperor: Satsuki Katayama.

As the only female minister in the current government’s cabinet, Katayama, 59, earned herself a place in the history books today as she became the first woman in modern times to officially witness the ceremony.

The Regalia Inheritance ceremony, which took place at 10.30am this morning inside the Imperial Palace in Tokyo, is traditionally off limits to all female members of the Imperial family, with neither the incoming nor outgoing empresses attending.

Katayama, 59, was the only woman among a small exclusive group of otherwise all-male guests, including representatives of three branches of government and adult male royals in line to the throne who witnessed the historic event, the first stage of Emperor Naruhito’s accession to the throne.

During the ceremony, the Imperial chamberlains entered the room and placed the state and privy seals, along with cases containing a sword and a jewel, two of Japan’s Three Sacred Treasures, on cypress wood stands in front of Emperor Naruhito as proof of his rightful succession.