In the Search for Kotlin, you will be requested to look for Kotlin in Tears of the Kingdom who has wandered off in his colorful hot-air balloon to places far and wide across Hyrule in search of Bubbul gems.
He needs these Bubbul Gems so that he can consume them and transform them into a Satori. Read on to find out how you can find him in TotK.
How to unlock The Search for Kotlin in Zelda: TotK
To unlock The Search for Kotlin, you will first need to complete The Hunt for Bubbul Gems side adventure in Tears of the Kingdom.
You can find both of these adventures to the north of Pico Pond which is southeast of the Great Hyrule Forest and down the road from the Military Training Camp.
In this quest, you offer Kotlin a Bubbul gem which you can find near Pico Pond.

After handing him over he will eat it but nothing happens so he goes off to find more of them. his older brother Kilton is here with Koltin.
When Koltin goes off to find more Bubbul gems, Kilton asks Link to look out for him and help him in turning into a Satori. Here is where the quest starts.
How to complete The Search for Kotlin in Zelda: TotK
The Search for Kotlin can be completed when you find Kotlin in Tears of the Kingdom. He can be found in the colorful stall.
As this stall is more like a hot air balloon, Koltin will fly around from one place to another using his stall. You can also move over to Tarrey Town and ask Kilton for Koltin’s Whereabouts. He will tell you where he is.
He can only be found during the night after 9 pm. He is found in different places throughout Hyrule but there are a handful of places where he appears in the night.
Location 1
You can find Koltin in the Hyurle field south of the Lookout Landing Skyview Tower in -0315, -0163, 0012.

Location 2
You can also look for him in 3658, 2066, 0168, Akkala Highlands. You can approach his stall either from the Ulri Mountain Skyview Tower move from the East Akkala Plains.

Location 3
Continuing your “Search For Kotlin” in Tears of the Kingdom, he is also found in Faron Grasslands, south of the Farosh Hills in 0581, -2685, 0112.

Location 4
He also appears in the South Tabaantha Snowfield in Eastern Hebra Mountains and it is nearest to the Orochium shrine in the coordinates of 1535, 2388, 0245.

Location 5
The next place is the Isle of Rabac, Eldin Mountains. It is located north of the YonoboCo HQ with the coordinates of 1438, 3088, 0397.

Location 6
The last place in your “Search For Kotlin” is in the Gerudo Highlands in Tears of the Kingdom. This will be southeast of the Gerudo Desert Gateway and South of the Turakamik Shrine with -2790, -2419, 0200.

When you visit any of the places mentioned above and find the colorful stall, approach it and talk to Koltin, he will tell you how hard it has been for him to look for the Bubbul gems.
He asks you to find more Bubbul gems and trade them for armor sets and important resources. When the dialog ends, the Search for Koltin will be completed in Tears of the Kingdom.
You can now visit him multiple times during the night in the places mentioned above and trade the Bubbul gems for the Mystic set.