I am no expert in this, but I have read that there are several ceremonies for what is called an Imperial Enthronement. There is no Japanese 'crown" at all. The Emperor takes possession of the 3 Sacred Relics of the Sun Goddess privately ( a mirror, a sword, and a necklace.) Later there is a traditional enthronement ceremony in which Emperor and Empress appear in ancient dress seated on elaborate throne structures in the old Palace at Kyoto are recieve homage. Still later, the Emperor alone observes a sacred ritual meal alone in a nocturnal ritual of the Sun Goddess.