Lone Shadow Longswordsman is an optional mini-boss found in the Ashina Reservoir area in Sekiro: Shadows Die Twice. He’s pretty aggressive and intimidating, but he’s also fairly easy to take down if you know what you’re doing.
Much like Seven Ashina Spears, taking on the Lone Shadow Longswordsman requires you to retrace your steps back to the early stages of the game. The Lone Shadow Longswordsman is actually waiting for you right where you started the game, at the bottom of the pit where you woke up. To get to him, travel to the Ashina Reservoir Sculptor’s Idol and head down the steps in front of you. Take out the two guards and the two wolves, grapple to the branch to the left, and then grapple again to the branch above. Then, jump and grab on to the tiled roof and shimmy along to the left a bit, this will allow you to climb up and drop down behind the pot banging enemy, but we don’t need to worry about taking him out. Instead, turn left and move to the edge of the ledge and you should be able to grapple across to the top of the pit.
There’ll be a friendly NPC here that you can speak to just next to the first hole into the pit, but this isn’t the entrance we’re taking. Instead, carry on moving forward and you’ll come to another hole in the ground. Look through the hole and you’ll see the Lone Shadow Longswordsman stood in the pit waiting for you. You’ll notice that he takes two deathblows to take him down, but if you jump into the hole and correctly position yourself above him on the way down you can hit him with a deathblow when you land, leaving yourself half the challenge.
From here on out it’s an all out brawl, and it’s all about breaking his Posture. Your ability to Deflect is going to be called into question here, and it’s going to be vital to keep you alive. He comes at you with a lot of quick attacks and combos, and you need to Deflect all of them until he tries one of his two Perilous/Red kanji attacks. Equally, make sure you attack him back at every opportunity if he stops attacking you – this is vital in preventing his Posture bar from completely recovering.
Speaking of Perilous attacks, the Lone Shadow Longswordsman has two of them. The first is a sweeping attack that causes him to move forward – when you see him start this attack, jump straight in the air and then jump again when above him to perform a Jump Kick and cause some serious Posture damage, and you should get a hit or two of you own in after too. His second Perilous attack is a straight kick that he charges up before performing; you’ll see him lift his leg and hold it in position for a second while the red kanji symbol appears – this attack counts as a Thrust attack, so you can use your Mikiri Counter to cause a lot of Posture damage and get another hit or two of your own in.
That’s really all there is to it. Stay aggressive and take the fight to him, deflecting his normal attacks, Jump Kicking his sweeping Perilous attack and Mikiri Countering his Thrust Perilous attack. Make sure you attack him every time he takes a step back so that his Posture bar doesn’t recover – if you give him breathing space you’ll be back to square one pretty quickly.
Other than that, your only real obstacle is the environment that you’re fighting in. The pit is very small with very little room for maneuver. Make sure you stay in the wider section where you found him waiting rather than the narrower tunnels and don’t let yourself get caught in a corner or the camera angle will prevent you from being able to see his attacks and time your deflections. If you do get caught in a corner, jump back into centre of the room as quickly as possible.
Follow all of these tips and you’ll soon break the Lone Shadow Longswordsman’s Posture and open him up for a second Deathblow.
Killing him will reward you with a Prayer Bead and some Scrap Magnetite, which can be used for crafting. There’s also a second entrance to the Abandoned Dungeon just through the tunnel behind where he was waiting, if you’re brave enough.