Khotun Khan isn't the final boss in Ghost of Tsushima.
Throughout the history of the game, it becomes clearer and clearer that the real adversary that Jin Sakai needs to face is Lord Shimura, his father figure.
The circle is complete, Shima has helped you take your first steps in combat, and he is also the last obstacle to overcome. The differences between the ideals of these two samurai being visibly irreconcilable. After writing a final haiku, the fight begins.
Duel against Shimura
This ultimate duel inflicts a penalty on you as you cannot change your armor: you are forced to use the ronin outfit, which, while not bad, is clearly not worth the samurai clan armor.
If you ever read this article before starting the last story quest in the game, consider upgrading this armor to the max — just like the rest of your gear. The only thing you can change is your talismans, which we advise you to do.
Shimura is a truly formidable adversary — even at the maximum level of legend, and having cleared the map of each region. He has many unstoppable techniques, and his thrust attack, although it can theoretically be parred, is incredibly hard to defend against. Its timing is really strange, and you have to wait for a little after the display of the blue glow to parry. You can also just block or dodge.
Shimura's unsheathed attacks are devastating too, they have immense range. In the end, the best way to win this duel is to be extremely aggressive and leave no opening for the boss. However, his charged thrust attack is an opening, the same for some of his unstoppable attacks. His drawn attack also becomes a big opening.
This will obviously not protect you from everything. We advise you to maintain the pressure with Guard Breaker (Triangle) attacks in Maximum Enhanced Stone Stance. As soon as his guard is broken, chain together several Heavenly Strikes to take his life away.
Kill or spare Shimura?
It only matters from a script point of view. The following cutscene is different, and then the dialogue with Yuna after the game credits are different, but it's nothing substantial. So you should choose the option you prefer. You simply get a different trophy at the end of the fight.
Original content by Robin "Raiden" Bouquet.