Oga Kaiten Training Base Remains

Oga, on the northern shore of Beppu Bay, became a training site for the Imperial Japanese Navy's kaiten manned suicide torpedoes in 1945. The Oga Assault Unit opened on 25 April. Training at sea depended on a shore establishment where personnel could prepare and maintain the weapons, making the surviving support facilities an important part of the site's history.

The town's historical museum describes repeated training in Beppu Bay during the war's final months. Personnel trained at Oga were deployed to Nishiumi in Ehime in August, but that unit reached the end of the war without launching an attack. The base therefore records preparations for suicide operations rather than a battlefield at this location.

Storage tunnels and other remnants survive around the former base. The memorial park near the former torpedo adjustment pool contains a full-size replica, installed in 2014; the park was completed the following year. This modern model helps explain the weapon's scale and must be distinguished from wartime remains. The nearby Kaiten Shrine also commemorates those who died in the wider programme.

The public park has visitor facilities and is free to visit. Access to the surrounding dispersed ruins is a separate matter: a 2025 town council discussion identified overgrowth and the need to assess their condition. Tunnel interiors are not confirmed open here. This approximate map marker follows the official tourism listing for the base-remains area associated with the memorial park, rather than identifying every surviving structure.