Which shrine in Nagoya holds the sacred sword Kusanagi?

The shrine in Nagoya associated with the sacred sword Kusanagi is Atsuta Shrine.

Atsuta Shrine, or Atsuta Jingū, stands in Atsuta-ku, Nagoya, in Aichi Prefecture. It is traditionally regarded as the repository of Kusanagi no Tsurugi, the sword that forms one of Japan’s Three Sacred Treasures. The sword is connected with the Shinto deity Atsuta Ōkami and with the legendary hero Yamato Takeru.

The shrine’s traditional history reaches back to the early centuries of Japan. In the Kojiki and related traditions, the sword became associated with Yamato Takeru and was later enshrined at Atsuta after his death. Historical and legendary accounts differ, but the shrine’s identity has long been inseparable from the sacred blade.

Kusanagi is not displayed for public viewing, so its physical form and present condition cannot be independently confirmed. That secrecy is part of its divine status. Hakkengū, an auxiliary shrine within the Atsuta complex, is also associated with worship of the sword, but the canonical answer to the question is Atsuta Shrine.