Throughout Genshin Impact's Inazuma region, there are a number of NPCs that players will encounter that will prompt a variety of unique world quests. One of the most rewarding world quests that Genshin Impact players can undertake is the "Treatment on the Island" quest located in Yashiori Island.
While this world quest is relatively quick and easy to complete, there is an additional secret achievement tied to the quest called "A Doctor's Odyssey." Players are able to obtain this achievement after the initial quest is completed and will be rewarded with a significant number of chests and Primogems. The only downside to this secret achievement is that while it is simple to complete, it requires the player to wait a total of three days before they are able to obtain all the rewards.
To start the quest, head to the Statue of the Seven location east of Higi Village. From this location, head northwest across the chasm to reach the doctor standing next to the cliffside. After speaking with Yasumoto the Doctor, he will task players with obtaining 12 Naku weeds.
After submitting the Naku weeds to Yasumoto, players must progress the in-game time to the evening of the following day. Players must then speak with the Doctor for a second time, which will spawn a series of Samurai that the player must defeat in order to complete the world quest.
After defeating all the Samurai, players will complete the world quest and receive 30 Primogems and 3 Heroes Wit. At this point, players are able to start the process of obtaining the "A Doctors Odyssey" secret achievement.
To start the process, head to the Doctor's cabin located nearby and interact with the bamboo basket in front of the house. After interacting with the basket, players will have the option to submit an additional 12 Naku Weeds. Place the Naku weeds inside the basket and return to the house in 24 hrs (not in-game time).
When players return to the location the next day, an exquisite chest will have spawned in front of the house. Players must now repeat the process of submitting Naku Weeds to the basket and waiting for 24 hrs two more times.
After players return to the Doctor's house on the third day, they will find that there is no chest in front of the house despite having submitted 12 Naku Weeds the day before. At this point, players must travel to three locations nearby to obtain 3 Pharmacist's notebooks.
PHARMACIST NOTEBOOK LOCATION 1
The first notebook is found on top of a group of stacked crates by the beach to the north of the Doctor's house.
PHARMACIST NOTEBOOK LOCATION 2
The second notebook is located on top of a rock next to the dirt road east of Fort Fujitou.
PHARMACIST NOTEBOOK LOCATION 3
The final notebook is found underneath a tree, guarded by Samurai to the north of Musoujin Gorge. After obtaining this final notebook players will unlock "A Doctor's Odyssey" achievement.
After players have successfully obtained all three of the Pharmacist's notebooks, players can head to the waypoint south of Jakotsu Mine to obtain their final reward, which is a luxurious chest.
Genshin Impact is available for Mobile, PC, PS4, and PS5, with a Switch version in development.