Oi was a Japanese light cruiser the keel of which was laid in 1919, launched in July 1920, and commissioned in the Imperial Japanese Navy in October 1921. The length of the ship was 152.4 m, width 14.2 m, and her standard displacement was 5,200 tons. The cruiser had a maximum speed of 36 knots. At the time of launching, the main armament was 7 140 mm guns in single positions, and the additional armament was, among others: two 80 mm cannons and four twin 533 mm torpedo tubes.
Oi was the fourth Kuma-class cruiser. Cruisers of this type were in fact the enlarged Tenryu class, but had greater range, speed, and better armament. In the interwar period, the unit served, inter alia, as a training ship at the naval academy in the city of Etajima (1928-1931), and after a short period of patrol service off the coast of China (1932), the unit returned to the function of a training ship (1933-1937). At the outbreak of the Japanese-Chinese war in 1937, the ship was directed to the line and covering Japanese landings on the Chinese coast. In 1941, Oi was converted into a torpedo cruiser. First of all, the armament of the ship was changed, the main element of which was as many as 10 quadruple 610 mm torpedo launchers! The unit took part in an action against the Aleutians in the summer of 1942, and shortly thereafter began to act as a fast transport carrier of the fleet, and its armament was reduced (from 10 to 6 launchers) in favor of strengthening anti-aircraft weapons. The cruiser was sunk on July 19, 1944 by the American submarine USS Flasher.