The Emperor will wear a traditional reddish brown robe called the "Kourozen-no-Gohou" that can be worn only by an emperor.
The robe was already used as attire for emperors in the 9th century.
It has patterns of paulownia, bamboo, phoenix, and the imaginary Chinese beast called "Qilin" woven in the cloth.
Emperor Meiji was the first emperor who wore the Kourozen-no-Gohou for his enthronement ceremony in 1868.
His predecessors, including his father Emperor Komei, wore a Chinese-style red robe called "benpuku" for their enthronement ceremonies.
Currently, Kourozen-no-Gohou is most commonly worn for rituals at the Imperial Palace.
The Emperor wore the attire a week after his accession to the throne in May for the first time. He performed rituals to report to his ancestors and various deities the dates of main ceremonies following his accession.