Crank the difficulty and play as a samurai instead of a ninja. Just straight rush every enemy you see. You’ll still probably have problems trying to complete all the assorted landmarks on the map, but the combat is way more fun when you and everyone around you die in 1-2 hits and you’re constantly swapping stances to stay alive.
Honestly, I wouldn’t do a replay, if I were you. I would just get the expansion pack and play that. If you’re really itching for a replay, you can do New Game Plus and at least earn New cosmetics instead of unlocking the same ones again.