Reach level 1800 or higher
Have Observation Haki V1 already unlocked
Go to the Third Sea
Travel to the Floating Turtle island
Find the Hungry Man NPC
Buy a Cup of Water from the Luxury Boat Dealer
Give the Cup of Water to the Hungry Man
Get the quest to find the Tushita puzzle
Complete the Tushita puzzle requirements
Defeat Longma
Obtain the Tushita sword
Talk to the Uzoth NPC
Pay 5,000,000 Beli
Obtain Observation Haki V2