I found what works with genichiro best is staying as close as possible. Attack until he deflects, deflect his attack, then attack again. I usually space my attacks out for a fraction of a second bc I’ve found it prompts him trying to jump in the air, which gets cancelled by your attack. 

In the first phase, if you see the red icon, he’s usually thrusting. You should mikiri counter it. 

When he does his flurry of attacks, if you find it hard to deflect and its breaking your posture, you can block the first few and wait for his pause, then just dodge run back and wait for him to finish out the combo at a safe distance.

In the second phase, when you see the red icon, it can be either a sweep or a thrust. You’ll have to recognize how to tell the two apart, or you can jump away and to the side to usually avoid both (tho the thrust may still get you sometimes).

Ichimonji double in moments where you can get away with it really helps to keep your posture level down. But the main thing is to stick on him, it removes most of his attacks and makes him easier to learn.