Old Hunter Yamamura or Yamamura, the Wanderer is a warrior from a distant land to the east of Yharnam. Yamamura pursued a beast for honorable revenge. When the beast led him to Yharnam he became a hunter of the League. Perhaps the beast he pursued was killed by League confederates. To confirm his membership of the League he was given a hat and staff. The League staff is the sign of a confederate, a directory within the hilt lists the names of fellow confederates. Members of the League brandish this staff to indicate themselves to fellow members of the League. The League is a secretive organization. Their members are only identified by this staff, indicating they were not accepted. Valtr, Master of the League makes reference to this:
“This bloody fate is ours alone.
Do not expect the world to grasp our work…
But remember, the confederates will always have my blessing…
And each other. Always.”
And the League Staff description:
There shall be no sympathy for those engaged in the bloody mission of the League.
No matter that an oath must be taken to uphold the illusion.
The League was a secretive organization, but their work was much too public and noticeable to other hunters so it is probable that members of the League were also Church Hunters. Yamamura has some telltale signs of adopting the culture of the Old Hunters in the employ of the Church. He wears the old hunter arm bands, wound tightly to prevent infection with the scourge. The old hunters believed in a number of hearsay claims about beast blood and the idea that the scourge was infectious is one such claim. They also believed that certain metals would ward off beast blood and that beast blood crept up the right leg, which led to double-wrapping belts around the thigh as a form of prevention.
Yamamura is found in the underground cell below the Grand Cathedral. The Church uses these cells as a place to hold hunters so that “things better left unseen, better left unknown, will decay quietly in the fallow darkness” indicating that those who find themselves in the cells have knowledge or traits that the Church wants hidden.
One day, the old hunters disappeared, and Yharnamites began to whisper of the hunter's sin. Drunk with blood, chasing after beasts, they would pass on to the Nightmare, every last one of them. Yamamura was no exception.
"Shrouded by night, but with steady stride. Colored by blood, but always clear of mind.
Proud hunter of the church.
Beasts are a curse, and a curse is a shackle.
Only ye are the true blades of the church."
This mantra must have been repeated often by those hunters about to engage in battle against the beasts as a means of calming their minds and giving them resolve. Without his wits, Yamamura repeats it to try and bring comfort to himself.
Which begs the question, what actually happened to drive Yamamura mad? We are told that when he stared straight into impurity, it drove him mad. The word impurity appears to reference vermin. The vermin description tells us:
Vermin, found hidden within filth, are only seen by League
confederates, and are the root of man's impurity.
Yamamura was a confederate of the League and so must have had the Impurity rune etched on his mind. The rune, discovered insider the forbidden beast eater, came from to symbolize “Impurity” and the oath of the League. Valtr will tell us
“By the oath of the League,
those who bear its rune will see vermin.”
Members of the League are able to see vermin where no one else can. They consider vermin, centipede-like creatures, to be the root or source of humanity's impurity. The League has assumed the task of finding and crushing all vermin. This must have been Yamamura's mission. But hunting vermin comes at a cost. Valtr will tell the player after they have crushed enough vermin:
“Your eyes say it all.
You've crushed vermin time and time again…
You've seen the filth that tarnishes the world of man…
Yet you are unbroken, you've the eyes of a hunter.”
He expects any who find enough vermin, to eventually 'break' or lose their minds. The player is seemingly a very rare exception to the rule:
“You have blessed the League with your presence.
This was my last, most pressing task…”
Whatever goals Valtr had, he was not able to achieve them without your help, even with all the League confederates backing him. Why crushing large quantities of vermin drives a person mad is unclear. It may be that they come to the realization that the struggle is futile, that vermin will always exist within humanity. Or perhaps they realize that vermin don't really exist at all, that they have been tricked into committing acts of atrocity. It appears that Yamamura had a revelation something like this during his time in the League, and it drove him mad. Perhaps his revelation is what got him locked up in the first place, we are only left to speculate.