Yes, it is possible to change your seat assignment.
To change your seat assignment, log in to the Check reservation page shown below and complete the necessary procedures.
「Check reservation」（Login page）
*You will need your reservation number in order to log in.
*Caution*
In order to change your seat assignment, it is necessary to pay the seat assignment fee.
When you request a new seat assignment, the seat assignment fee you have already paid is not refundable.
Seat assignments can be made up to 5 hours prior to the departure time.
<Highlight>Reference</Highlight><GrayLink>What is a reservation number?</GrayLink>