Since you’ve provided cargo insurance to Ichikoh, we can go ahead claiming a refund to CNA.
First duty of the insured (JAS) is to hold the carrier – or any third party involved in the transport – liable for the loss and so, to provide such letter/email to me in order to provide the same to the insurers. This must be done for recovery purposes.
Secondly, for such amounts, underwriters will surely request to inspect the goods.