In 1944, two of the surviving 5,500-ton-type CLs were converted to CLAAs.
Isuzu was one,
Ayase was the other. By this time,
Ayase was the sole survivor of her eight-ship class; all her sister ships had been sunk (
Naka,
Otonase, and
Jintsu in 1942,
Minase,
Kako, and
Sendai in 1943, and finally
Naniwa in February 1944). She completed her refit in September 1944, and was part of the supply convoy to Lingga that November. From January 1945 onward, she remained in the Singapore area, and when
Isuzu was sunk in April 1945, she became the sole surviving pre-1940 CL. The modification gave her several updates, including replacing her main armament with four twin-mount 127-mm. Type 89 Mod A1 guns. This actually saved weight:
Original Armament (as completed): 7 x 140-mm. Type 3 shielded single-mount guns; each mount weighs 20 tons apiece for 140 tons total.
Armament as of 1944 CLAA Conversion: 8 x 127-mm. Type 89 A1 Mod. 2 unshielded twin-mount guns; each mount weighs 20 tons apiece for 80 tons total.
As one of three Japanese cruisers still in Malayan waters, she was a prime target for British forces in the Indian Ocean, managing to outlast both
Haguro and
Ashigara, but anyone could see that her luck would not hold out forever. Finally, on 28 September 1945, she was en route back to Japan when she and the convoy she was escorting were surprised by a British surface group centered around battleship
H.M.S. Lion. As the merchants scrambled to escape, pursued by the British destroyers, the Japanese escort ships bravely challenged the heavier units in a suicidal delaying action, with
Ayase challenging
Lion directly. However, the contest was a foregone conclusion;
Ayase took five direct hits from
Lion's sixteen-inch guns, with the last one detonating a magazine; the old cruiser disintegrated in a massive fireball and sank with only 13 survivors. Afterward,
Lion's captain commented that the fight "...just proved further the fighting samurai spirit of the Japanese people."