Deleting your Suica from your Wallet app will save the card to the server. A Suica saved to the server can be reconfigured on the same device or transferred and reconfigured on another device. 

[Steps to delete a Suica (iPhone)]
· Launch the Wallet app
· Select the digital Suica card you would like to delete and tap the three dots "..." button in the top-right corner
· Tap "Card Details"
· Tap "Remove Card"

[Steps to delete a Suica (Apple Watch)] Performed on the paired iPhone. 
· Launch the Watch app
· Select the Suica you would like to delete from "Wallet & Apple Pay"
· Tap "Remove Card"

[Steps to delete a Suica (device unavailable)]
Contact Apple Care and explain that you want to know how to delete your Suica from the Wallet app on an old device.  
If you have any questions or issues with the steps above, please also contact Apple Support for assistance.