I don't think Isshin uses the Way of Tomoe. As seen by Genichiro, the lightning goes to him. Even swerving and reaching him from under a roof. https://youtu.be/sobpYAN5iuc?t=250
Isshin rather catches a falling lightning bolt on his yari. It implies he's just so good that he can predict when it'll strike and position himself to weaponize it. https://www.youtube.com/watch?v=OYvezpDncQY
Of course, it begs the question where the lightning came from. Maybe coincidence. It's like if Gael summoned lightning or not.
I don't think Isshin uses the Way of Tomoe. As seen by Genichiro, the lightning goes to him. Even swerving and reaching him from under a roof. https://youtu.be/sobpYAN5iuc?t=250
Isshin rather catches a falling lightning bolt on his yari. It implies he's just so good that he can predict when it'll strike and position himself to weaponize it. https://www.youtube.com/watch?v=OYvezpDncQY
Of course, it begs the question where the lightning came from. Maybe coincidence. It's like if Gael summoned lightning or not.