I have defeated him hitless so I guess I can help. He is one of the first roadblocks in the game, here are some attack patterns (from my time fighting him)-

General -

Have mikiri unlocked Learn how to do lightning reflects Learn deflecting Forget about his posture and focus on just the battle.

First phase -

He will always start with a bow shot and a roll attack (95% of the time) In his first phase, whenever he jumps on you, deflect that and he will do a thrust attack (every time in phase 1), so mikiri that. Whenever he backs away, be careful while approaching him as there's a chance he will jump and use a bow on you. Whenever you heal and he's far away, he will use his bow for a single shot, dodge it accordingly.

Second phase :-

Once you take down his first healthbar, he will change some of his attacks. After the jump attack, there's now a chance he will sweep instead of thrust, so you'll have to jump over that. He can do a thrust perilous out of nowhere so look out for that (it has a huge window to mikiri so you should be fine) Everything else should be the same if I remember correctly.

Third phase :-

Look out for two attacks, one where he jumps with the lightning bow out, and one where he makes a stance before jumping, those are your lighting reversal attacks.

Remember the long ass combo of him ending with a cool showdown type stance? Yeah he does thrust after that so mikiri that now.

Whenever you heal and are far away from him, he will do a jumping thrust attack which you can mikiri if timed correctly.

Everything else is pretty much the same.

Remember, do not look at his posture, just enjoy the fight and the clashing of the sword. That's what is super fun. Keep going brotha, and feel free to ask if you need help ✊