Yeah, as far as I know sunken ships are generally struck from the register rather than decommissioned. And unsurprisingly, the IJN was often unwilling to officially admit that one of their ships has sunk, which in effect is what striking from the register means.
Everyone: 「Akashi-san. Thanks for your hard work」May 10th, 1944Akashi's decommission dateThe pleasure is mine! I'm glad I could repair everyone!