Kirin is one of Monster Hunter's most iconic creatures. It was introduced in the original Monster Hunter game for PlayStation 2 in 2004 and has been a staple of the series ever since.
But the creature's quest in Monster Hunter: World is hidden and can only be unlocked after completing a few optional quests where the player attempts to capture four different monsters in multiple regions.
To unlock the low-rank Kirin quest, you have to talk to the biologists in Astera (just left of the main gate, near the capture area) after completing the Odogaron main quest.
These are the quests you'll need to complete.
1) (Two stars): Snatch the Snatcher (capture Kulu-Ya-Ku).
2) (Three stars): Landing the Landslide Wyvern (capture Barroth).
3) (Four stars): White Monster White Coat (capture Paolumu).
4) (Five stars): Man's Best Friend (capture Odogaron).
Once you've completed the four optional quests, a new quest will unlock after talking to the Impatient Biologist in Astera. It'll be a five-star optional quest that will unlock Kirin.
Kirin is essential to some players who want to upgrade their armor and weapons at later levels. To unlock Kirin in high-rank quests, however, players need to beat the story and reach the Hunter Rank of 49. A nine-star quest for Kirin will then become available.
Players can also complete this quest by searching for an SOS Kirin quest flare by joining other hunters to help them out. After beating the quest for the first time, it'll change into an eight-start optional quest that can be repeated as often as you like.