Nippon Budokan (日本武道館), located in Kitanomaru Koen Park which used to be part of former Edo-jo Castle, was constructed for the judo competition in the 1964 Summer Olympics. Its name literally means "Japan Martial Arts Hall" in English.
On the second Monday of January, a martial arts event called the Kagamibiraki-shiki & Budo-hajime (鏡開き式・武道始め) is held here.

Kagamibiraki-shiki & Budo-hajime at Nippon Budokan Hall

On Coming of Age Day, a national holiday which is held on the second Monday of January, a martial arts event called the Kagamibiraki-shiki & Budo-hajime is held at Nippon Budokan.

After some ceremonies, the Yoroi Kizome is conducted in armors of the Kamakura period (late 12th century to early 14th century). The Yoroi Kizome is a ritual practiced when a warrior obtained a new armor or when he wore an armor for the first time.

The sankon-no-gi is a ceremony conducted before warriors head for battles.

The Kagamibiraki-shiki is a ritual to break kagami mochi (a rice cake decoration for the New Year) in the end of the New Year.

Shusujin-shiki is a ceremony conduted before heading for a battlefield.

Participants clad in armors circle the ground.

Next, there will be demonstrations by leading experts of Kyudo (Japanese archery), kendo, karate, naginata, sumo, jukendo, aikido, shorinji kenpo, and judo. These are marial arts developed in the modern era as sports from the maritial arts in the feudal times which were techniques to kill (or neutralize) opponents.

After that, the first joint practice of the year takes place.