I hated Nioh 3's samurai style until I discovered one easy-to-find upgrade that helped me learn to love the art of the Ki Pulse
The Samurai style in Nioh 3 is much closer to the methodical, more hardy, planted sword master that you'd expect from a soulslike, at least compared to the shadowy ninja. However, Nioh 3's samurai has one defining factor that makes it hard to get to grips with for newcomers: Ki Pulse.
Ki is effectively your stamina, and you'll soon be breathless if you start flailing around as the samurai. So much so that I barely used the warrior early on in favour of the ninja, where I simply overwhelmed the enemy with a flurry of attacks and dodged here, there, and everywhere.
The Ki Pulse is how samurai manage their stamina, requiring you to press the right bumper on a controller at the correct time during combos to recover Ki. It's a lot to keep track of, and it doesn't lead to very smooth, impactful samurai combat if you can't do it right. Plus, I'm a sucker for odachis—large, Ki-eating swords—so I was burning through stamina after just a few hits, leaving me defenceless.
One early item that really helped me is the Running Water skill, which lets you perform a Ki Pulse by dodging. It's as simple as it sounds, but it's another way to get your stamina back after a combo while also evading attacks. I won't say no to an extra tool in combat.
You can find this skill in the Hamamatsu Castle Crucible (the nightmare realm you'll enter a short way into the story). Once you reach the point where rock platforms come out of the lava, head into the building to your right. Then jump over the platforms on this side, kill the enemy that pops out of the mist, and then open the large red chest. There are two other skills I recommend grabbing while you're in the area; they'll also come in handy for the Jakotsu-baba boss fight coming your way.
Of course, there's no substitute for mastering the Ki Pulse, even with the Running Water skill. I recommend increasing your heart stat and unlocking the Flux and Flux II skills on the right side of the Samurai tree to enable you to switch stances mid combo while also triggering a Ki Pulse. It's the gateway to long, deadly combos.