In 2004, one of our members visited Yahiko Jinja in Niigata, Japan. There was a sword museum next to the shrine which housed two of Japan's biggest swords.
Odachi Masayoshi, 7 shaku 4 sun. Nakago 3 shaku 5 bu. Forged by Sanke Masayoshi 1844 (14th year of Tenpou).
There is however some other information online that needs clearing up:
These two links show an odachi called the Norimitsu Odachi, the longest sword in Japan, and is displayed at the Kibitsu shrine in Okayama-ken. It was forged by 三家正吉 Sanie Masayoshi (dated 1843) Blade length: 224 cm.
It's unclear if these two swords (the one displayed in Kibitstu shrine and the one at Yakiho shrine) are the same sword.
Shida Odachi, 2.204m long blade, nakago 1.018m.
Other items displayed at the museum: