Buso Ability, also known as Armament Haki, can be bought from Old Man Silver (Buso Trainer) at Logue Town for 100k after reaching level 350.
-When activated (J) Buso will make your hands fiery and you will now be able to use physical attacks against elemental fruit wielders. It also is great for PvP and sometimes required for PvE.
Buso V2 is Located inside a rock house on Revolutionary Island, the minimum requirements are level 1150 and 250k.