Probably Spear or axe. They all scale with constitution and they can cover the tonfas' lack of reach.
Does this game have a story? I created then it threw me into a tutorial then instantly to a map. It was a bit jarring lol.
It does. It's basically a fantastical retelling of the unification of Japan under Oda Nobunaga in the late 16th century, but unless you are versed in Japanese history it'll just seem like a bunch of cutscenes thrown together after you kill bosses.
You don't really play Nioh for the story.