This mini-boss is located in the garden past the bridge with the two shield-wielding enemies, right before you reach the Bamboo Thicket sculptor’s idol. There are a lot of normal enemies in the surrounding area so it’s recommended to deal with them first, even if you aggro the mini-boss. Just do some hit-and-run tactics until he loses interest. That way, you’ll have the entire field yourself to sneak around and land a deathblow on him.
How to defeat this boss?
As with most mini-bosses, the first step should always be landing a stealth deathblow. If you took your time clearing the entire field of enemies, you’ll have the freedom to choose when to sneak up on him.
Fighting him on even terms can be difficult, thanks to his spear’s range and his perilous thrust attack. If you have learned the Mikiri Counter, this battle can be ended in mere seconds. Press Circle just as the enemy thrusts his spear and Sekiro will step on the spear instead, allowing you to follow up with an attack and deal high posture damage to the enemy, or better yet, a deathblow.