William heads toward Itsukushima island of Aki province to deal with infested yokai and pirates to get Kobayakawa assistant. Move ahead towards the shrine and speak to the woman standing to the left.
Mission – The Ocean Roars Again
The area has shipped with pirates, you can go on it to take them down or else you can take the passage on the right of a shrine. Walk straight inside, fight with pirates in the path. The place has the bonfire, you will need to find them one by one and burn it. The first one is on the right side where you killed the first pirate.
After burning the first one you will see a second one ignited at the far end. that is the next place you need to go. Walk through the broken wooden platform. Watch out for portable versions of Umi-Bozu a water demon. Near the fire, you will encounter more of these demons with other yokai.
For the second one, you can take the roof top, there is a broken one. You will need to jump down defeat a yokai and then burn the bon fire. The exact location is just on the left side of a ship with blood grave on it. For the third one gets down on the left of a shift. There is a passage with clothes hanging on the top.
Move ahead to a door on the left side. It will take you to the form with the final bonfire. Fight with few demons and finally burn the bonfire. Run towards the main gate between two fires for the final boss fight, a giant Umi-Bozu. The demon will dive on different locations. You can use arrows and weapons that can cause damage from a distant. Another thing, once the demon dives near the platform run towards it and attack him. It will be a long fight. After losing almost half of its health it will dive up, you can then attack it.
Umi-Bozu will take a long time to die. Just avoid staying in direct attack range if you are loosing health and Ki. After the demons death, the mission objective is over. There are three platforms around with fire in them. Reach them and use your weapon to fire it.
So this was the end of Chapter 6 The Ocean Roars Again, William defeats Umi-Bozu and frees the land from infested demons and pirates. You can continue with our Nioh Wiki guide or continue with Chapter 7 Spider Nest Castle Walkthrough.