Follow these steps to move a Suica from your Apple Watch to your iPhone. Ensure you are in an area with a stable network connection. Note that a single Suica cannot be used on your iPhone and Apple Watch at the same time. Moving a Suica between devices may change the Suica ID number. 

1.  Launch the Watch app on the paired iPhone.
2.  Tap "Wallet & Apple Pay."
3. Select and tap the Suica you would like to move to your iPhone from the list under "Payment Cards on Your Watch."
4. Under the Info tab, tap "Add card to iPhone."
    

If the operation is unsuccessful, contact Apple Care for support.