Frog on my koi!

Hi

Just been out to feed the fish and noticed that my large koi has a frog
attached to his head!
I have tried to get it off the fish but seems to be clinging on for dear
life.
The poor fish seems to be trying to flick him off and seems uncomfortable as
the frog seems to be clinging on my the fish's eyes (ouch)!

Has anyone else had a similar problem and know whats is the best solution.
ie leave it alone or keep trying to get it off

Many thanks


Cheryl