Sekiro: 10 Helpful Tips & Tricks To Defeat The Final Boss
7. Be Patient And Don't Get Greedy
This can be a long fight, you need to be smart and conservative.
When the opportunities present themselves, prioritise healing over getting a few extra hits in.
A good idea is to observe the rule of two, especially in the first Isshin round when he just has his sword, and he's doing his standard attacks.
Obviously this won't work for his un-blockable attacks.
If he ever leaves himself open just hit him twice then instantly block. If he's parrying your blows, again, just hit him twice then block (doing posture damage is more important in this fight any way).
If you try to fit in any more he will just hit you back and do way more damage.
So it's 1, 2, block, let him do his attack then 1, 2, block.
Retreat if you need to restore posture and health.