This guide will provide you with all the Haki locations in King Legacy.
There are only three Haki that you can obtain by purchasing it from their dealers: observe, armament, and teleport.

You can purchase a teleport in soldier island inside a spawn house with a brown roof for 50k Beli.

Any level can purchase any of this Haki, but you need belis.

You can purchase an observation Haki in Sky Island for 1.5M beli.

You only have eight dodges; after that, you will take the NPC damage.

When you use logia fruits and observe, the dodges will remain eight; however, when NPC has armament, they can now break your ken and damage you.
You can purchase armament in Bubble Island for 500,000 Beli.

Buso Haki will increase your fighting style and sword basic attacks and special skills.

It will not increase devil fruit damage except for some dough fruit skills.
Buso will coat your arms or legs if you have a dark leg fighting style with a shiny coat.

You can also obtain another Haki, but you cannot purchase it from any dealer. The other Haki is conqueror Haki; this Haki can stun players or NPC.
You can only obtain conqueror Haki through a game pass for 2,500 Robux.

But there is a 0.1% chance of getting it when the player joins for the very first time.