45, was an Imperial Japanese Navy Kaichū-Type submarine, the lead unit of the Kaichū IV subclass.

The submarines of the Kaichu IV sub-class were an improved version of the preceding Kaichu III subclass, slightly larger, with heavier torpedoes, and with the deck gun mounted forward of the conning tower instead of aft of it.

For surface running, the submarines were powered by two 1,450-brake-horsepower (1,081 kW) Sulzer Mark II diesel engines, each driving one propeller shaft.

[2] Launched on 18 October 1921,[2] she was completed and commissioned on 25 January 1923,[2] the lead unit of the Kaichū IV subclass.

[3][4] Her crew lost control of her, and she sank to the bottom in a vertical position in 170 feet (52 m) of water.

[2] This lasted until 1 December 1925, when the division returned to Submarine Squadron 2 in the 2nd Fleet.

[2] On 1 December 1926, Submarine Division 14 was reassigned to the Kure Naval District, in which it remained until 1933.