Announcement reposted from Amazon Japan:
Amazon Partnered Carrier options allows FBA sellers to use shipping service for shipping products to domestic Amazon fulfillment centers at discount rate.
We are offering a new discount promotion from December 5, 2023 through March 31, 2024. During this promotion, FBA sellers can use Amazon Partnered Carrier service (Yamato) at a discounted rate without registering in advance. We will also raise the weight limitation of each parcel for Amazon Partnered Carrier program (Yamato) so that more sellers have opportunities to use this program.
For more information about this promotion see FBA Partner Carrier Prgram promotion (Japanese).