there's a lot to say about figuring the pattern to this one out and descriptions this long will be more commonplace with these final uploads with emma, it's mostly about deflects. the majority of your damage here comes from baiting her grab and ashina cross then following up with your own attacks. i normally avoid using combat arts or prosthetics as much as i can but the bell demon buffs to the late game boss health and posture makes doing these without them an ordeal isshin here is much simpler than his sword saint fight. focus on consistent parries and watch his feet - when he drifts left and swings right a block or a dodge triggers him to initiate a throw, a parry will not. he also throws if you attack while his blade is pointed to the ground and he starts moving right though half the time it also triggers a horizontal spin. either way, a quick single attack baits him - dodge backwards once and then again immediately once you see that he's starting a throw. this gives you just enough spacing to counter him perfectly in both phases dodge to his right the moment you see his shoulders shrug during his ichimonji. you can run from his charged attack where he holds his sheathed sword up but if you hit him with a combat art you can interrupt it instead. there's an audio cue - he vocalizes when charging, letting you know to run or attack he didn't do it here thankfully but he has a flame attack in phase 2 that has excellent tracking. jump, not dodge, to the right of this just before it lands be patient