Haki

Overview
There is currently one type of haki in-game called Buso haki. Haki was first introduced in one piece. In the game you can buy buso haki for 1 million beli from the armament haki seller at monke island

How to obtain
To obtain you can climb the pillar the second u see after the docks, jump on the tree and you should go a few more trees unless you climbed the other side which you should see the armament haki seller.