Shahed drone's are not serious weapons of war. Japan could easily produce millions of them if needed. The drones are good for antagonizing and terrorising a civilian population. A few F35s and bomber squads could reliably deplete and destroy the entire Iranian drone stock and manufacturing capacity if there was the desire and higher tolerance for civilian casualties.

In other words if Japan were in a position where they were willing to use drones to indiscriminately attack soft targets an F-35 would be about a trillion times more effective.