Nioh

This is the hardest trophy in the DLC. You must have first unlocked Way of the Demon, which is done by completing most missions on Way of the Strong to unlock 'The Queen's Eyes' which upon completion will unlock Way of the Demon. You must then complete all missions in Siege of Osaka (Summer) on this difficulty. The Twilight Mission is not required.

If you have completed the main game and/or Dragon of the North/Defiant Honor on Way of the Demon then this shouldn't prove too difficult for you. I also strongly recommend finding all Kodama on Way of the Samurai so you can use the Healer Blessing on Way of the Demon to make elixirs drop more often.

I have linked a post from my Dragon of the North Guide: LINK, which provides in-depth tips for completing Way of the Demon missions and the same principles apply here. I highly recommend checking this out if you are yet to tackle the Way of the Demon.