Ashina Reservoir is introduced as the Prologue in Sekiro: Shadows Die Twice.
Your task is to get to the building and save the Divine Heir from the guards.
Here’s a walkthrough of Ashina Reservoir (Prologue) in Sekiro.
Climb out of the cave
You will start the game at an underground tunnel / cave. Keep running forward and jump out of the cave.
The words Ashina Reservoir should appear.
Go through the ledge
Keep going until you reach this ledge. Hug the wall and walk to the other side.
Stealthily avoid the guards
As you’re unarmed, you have to avoid detection from the guards.
Get to the tall grass and crouch while walking.
Stay alongside the wall and keep walking towards the building.
You will then reach a small hole at the building. Go through it.
Under the house, you can eavesdrop to hear what the guards are saying.
Keep going ahead.
Find a way to the Divine Heir
The Divine Heir is held captive in his house. Find a way into the place without getting caught.
Don’t go towards the guards. Find a way where’ll you reach a ledge where you have to hang on it and shimmy to the other side.
You should now reach the bottom of the house.
Climb inside through this crack on the wall.
A cutscene will load where you’ll meet the Divine Heir. Wolf (your character) will be given a katana named Kusabimaru.
You can now use a katana after the cutscene.
You should also get a Healing Gourd. This will come in handy to restore your health, but the use is limited.
Next, climb upstairs and you’ll find a healing pellet.
You can equip your healing items as “Quick Items” in the menu. It’s probably under the Equipment section.
Get to the secret pathway
The Divine Heir will tell you to find the secret pathway, and let him know when you’ve done so.
You can use the front door and go out of the building, if you don’t mind fighting the guards.
At this point, combat should be fairly easy, but it’s still easy to die.
Get to the gate with the two guards. Kill them both. Just parry or block their attacks and kill them quickly.
Defeat Leader Shigenori Yamauchi
Keep going and you’ll face Shigenori Yamauchi. He’s sort of a mini boss.
It isn’t too difficult of a fight yet. Wait till you meet the next mini boss.
Once you’ve defeated him, find a way to get to the bottom of the place.
You may find another item here.
You should see a bridge from a distance. Get towards it.
Climb on the ledge below the arch and slowly get to the right side, avoiding detection.
You will encounter this guy under the bridge. Kill him.
Continue going downwards.
Keep going down until you see this door with a lamp. This is the secret pathway.
If you go through it, you’re pretty much done with this place for now.
A cutscene will load and the Divine Heir will follow you.
Continue following the path upwards.
Fight Genichiro Ashina
You will meet Genichiro Ashina, a boss you’re not supposed to defeat in this Prologue.
So don’t bother if you die here.
In the cutscene, Genichiro slices off Wolf’s left hand. Wolf then wakes up sometime later with a prosthetic one.
You’ll learn more from the scene.
You can now use the Shinobi Prosthetic in the game. It’s useful for grappling and other movements.
You can ask the man who helped you more on what he knows.
And that’s pretty much it for the Prologue in Sekiro: Shadows Die Twice.