This is a Side Tale in the Iki Island Expansion for Ghost of Tsushima: Director’s Cut. These are completely optional but if you’re aiming for all Trophies, must be completed towards that goal.
Meet Sugi by the old fishing village
Before you can begin this Side Tale, you must first complete the Troubled Waters Tale, this will then become available. Once it is, make your way to the north of Gonoura Cape to meet with Sugi, the nearest Fast Travel points are the Blood-Stained Shrine or the Viper’s Den. Once you reach the location, you’ll notice that Sugi is nowhere to be seen and a group of enemies are instead here. If you’re unseen, make use of a Stand-off to cut them down and then head down to the pier to rescue a captive and Sugi will reveal herself, speak with her to begin the Tale.
Defeat the Mongols and Yamaneko’s Crew
To begin with, you’ll need to deal with the lookouts nearby, head north, scale the cliffs and simply deal with the three enemies positioned up here before resting at the campfire. Once nightfall comes, you’ll need to survey the three points of interest and then find a way to signal Sugi. Drop down below, assassinate the Mongol near the campfire and then interact with it to signal Sugi, causing her to use the hwacha to rain down fire on your foes.
This will allow you to deal with the first group of enemies easily and once they’re defeated, you’ll spot another campfire to use as a signal on the cliff up ahead. Take care of the Mongol at the bottom of it and then climb up, kill another and signal Sugi once more. Watch as she uses the hwacha once more to deal with this group (and finish any stragglers with your bow) and then proceed along the rocks to the east to the next campfire.
You’ll need to use your Longbow once you’ve grappled over to deal with the Archer overlooking the campfire, then get close and use a Chain Assassination to deal with the others up here. Once clear, Sugi will attack on her own with the hwacha and you’ll need to assist her with clearing up whatever Mongols are remaining. Use your vantage point and Explosive Arrows to deal with the Shamans, and then drop down to finish up any that are still alive after the hwacha’s fire.
With the Mongols and Yamaneko’s crew defeated, all that’s left to do now is to regroup with Sugi up the coast. Follow the coast to the north and you’ll find no sign of Sugi at the campfire. When morning comes, examine the debris and you’ll find her hat washed up, implying her death and concluding the Tale.
Despite the Tale being technically over, there is still more to this story. Fast Travel to Thieves Rest Village on the east of Iki Island and you’ll find a raider strapped to a tree with a note pinned on him. Examine it to learn that Sugi survived and has decided to leave the village, for learning this, you’ll obtain Sugi’s Kasa Hat as a cosmetic to wear.