The Rage God's Mountain

Legends tell of a young boy by the name of Tsujo Shikaeshi who long ago lived peacefully under the shadow of Gekidoyama Mountain, before it was granted that infernal name. The base of the mountain had served as the Tsujo family's ancestral home for seemingly endless generations, since eras before history itself; they had prospered thanks to the natural blessings bestowed upon them by the bountiful mountain, until one fateful night that down from the mountain's peak came their demise. Not long before the Advent of Sin, a twisted and warped rage beast managed to squirm its hideous form into the mortal world. Its abominably mangled mass of mouths and limbs shambled their way down the mountainside, leaving a trail of destruction and carnage in its wake.
It was not long before the revolting rage beast reached the Tsujo's multi-generational mansion, and the family did not stand a chance. Its wildly flailing limbs tore through the stone walls surrounding the mansion, and then through the wood and paper screens inside. The men of the family took up arms to fight while the women took the children to flee, but with a swift snap of its knuckly fingers, each man was reduced to an unrecognizable, gory mush; then with incredible speed, it wrapped its sinuous digits around the throats of all the women and, with a flick of its countless wrists, it popped off each and every one of their skulls. The children screamed in terror as the grotesque rage beast stuffed its endless maws with the still bodies of their mothers, cousins, and aunts. The children all wept, broken in despair, all except Shikaeshi, whose lungs burst with thunder as he vehemently cursed the beast before him. He swore that the wrath of the gods would befall the vile demon as it slowly, one by one, devoured the children around him whole until he was the only one to remain.
Shikaeshi continued to shout threats as the oblong beast and its menacing maws encircled him, bearing thousands of sharpened smiles all dripping with the blood of his family. Just then, one of the mouths began to cough while the others laughed with the voices of children. The one mouth hacked and wheezed and then vomited forth a katana of bones that fell before Shikaeshi's feet. Terrified but not petrified, Shikaeshi grabbed for the blade, but then, just as quickly as the demon had come, it retreated, slithering its way back up the mountain the same way it had come down, leaving rut in the earth matching its blasphemous form.
Shikaeshi blinked and beheld the devastation all around him. His home was in ruins and his family was gone, slaughtered and devoured by a horror beyond his comprehension. All that was left was the bone katana. By instinct, he knew that the blade was cursed; even so, when he held the osseous hilt in his hand, he could almost feel the heartbeat of his mother, his father, his brothers, his sisters, and all the others he had lost. He thought for a moment that perhaps by burying the blade he might be able to set their spirits to rest, but then, from the back of his mind, he recalled the image of the innumerable laughing faces that had swallowed everything whole. His heart was hardened. He swore that one day he would use that cursed blade to slay the demon, and so he hid it away so that no one else may come to claim or cleanse it. 
== Aftermath ==
The second morning after, Skikaeshi's paternal grandparents, the only two members of his family who had not been in the mansion that night, returned home from their vacation at a nearby hot spring inn to find that the world they had worked their whole lives for was utterly destroyed. Only one fragment of that world remained, Young Shikaeshi, who alone was working solemnly to make markers to memorialize each and every one of their annihilated kin. His grandmother collapsed to the ground in tears, clutching onto the dirt and grass as if it were hands of all her loved ones slipping away, while his grandfather gazed on with an empty stare; meanwhile, Shikaeshi continued to work on the markers without so much as turning to acknowledge the two. After a moment of silent mourning, Shikaeshi's grandfather walked over to him and placed his hand on his back, saying, "That's enough for now." Shikaeshi grabbed onto his grandfather's wrist and shoved it away. The two spoke not a single word and remained motionless for some time before the grandfather continued, "Come, we need to help your grandmother find a place to rest."
Shikaeshi and his grandfather lifted his grandmother off the ground, and together they walked back to the hot spring inn. As it so happened, the inn was owned by Tomo Kuyami, a respected philanthropist and a close friend to the Tsujo family. Upon hearing about the tragic fate of the Tsujo family, Tomo welcomed Shikaeshi and his grandparents with open arms. They could stay as long as they needed so long as they helped out a little with the business here and there; Shikaeshi's grandfather bowed gratefully and accepted. 
Shikaeshi and his grandparents were treated as part of the Kuyami family, and it was not long before they had finished their mourning and they began to settle in, but Shikaeshi's thoughts were still completely clouded with visions of the horrors he had witnessed that night. He went about his days in a daze, doing his chores with his body while his mind was absent, alone, and afraid someplace far away. Every night when he closed his eyes, he could see the gruesome maws dripping with his family's blood and, he could hear the roaring laughter of the demon as the souls of his loved ones screamed while their mangled corpses twitched inside the belly of the beast. He was miserable, but his sadness subsided with fear and his fear was cleansed through rage. Shikaeshi realized that if he was angry, he would not feel afraid, and he clung to his anger to give himself some kind of hope to carry on. He had sworn vengeance and divine wrath on the beast, but he needed determination and fervor to enforce this will. He stayed angry to stay powerful, and whenever his heart would waver, he would promise himself that he would avenge his family no matter what.
From that point on, Shikaeshi became much more lively and would take time each day to practice with a blade; each night, he would meditate in solitude, performing small sacrificial rituals for those he lost. As Shikaeshi matured, Tomo's daughter of a similar age, Ritsu, who had long ago taken a liking to the boy, could conceal her feelings for the fine young warrior he became no longer, and in time she opened her heart and made her intentions clear. Shikaeshi was reluctant at first, but with the encouragement of his grandparents he accepted her feelings; however, he insisted that he must first exact his revenge against the rage beast. This, his grandfather did not approve of, and he urged Shikaeshi to not seek vengeance but to just let his family rest. His grandfather expressed that he was proud that Shikaeshi had become more powerful, especially because now he had the strength to protect those he loves and prevent any more tragedies, but his grandfather did not wish for Shikaeshi to risk his life needlessly against the dangerous beast which had not stirred once since it came down from the mountain that night. Shikaeshi, bearing the weight of all the promises he made to the dead and to himself, refused to listen to his grandfather. He continued his training regiment with more zeal than ever before and prepared for the day that he would face the demon. Ritsu was worried for Shikaeshi, but, nonetheless, she promised that she would wait for him to be ready and allowed him to continue to walk the path he chose.
== Confrontation ==
While Shikaeshi had not told a single soul which day it was that he intended to set out against the demon, that morning, the day of the Celestial Festival, the inn was visited by a robed and hooded figure who revealed himself to be the legendary Master Jitsu, the Wise Priest. He asked to speak with Shikaeshi in private, and silently Shikaeshi nodded his head in consent. The two of them walked far into the woods and they sat upon stones facing one another as Master Jitsu spoke:
"You are probably curious as to why it is that I have come to you today. Well, the truth is that I have not come to give you a blessing for your upcoming fight against the darkness, but rather I have come to reproach you and give you an order to step back into the light... You remain silent, but I can tell from the daggers in your eyes that you have no intention of abiding by the edicts of an unfamiliar priest. In truth, I must say that I have not come here as an ally. As far as I am concerned you are already a beast far more dangerous than any demon. The animosity on your brow does little to convince me otherwise.
I have not come to show you love, for that you already have in abundance but have chosen to ignore for so long. You hold so desperately onto the love that was lost that you refuse to accept the bountiful love all around you. You probably still count yourself as a miserable soul, but, truthfully, there are few quite so fortunate and blessed as you. You probably will denounce me as a lecherous old man, but if I had a young beauty as fair as that Ritsu Kuyami confess her love to me when I was your age, well I likely would never have never been able to take my vow of celibacy, to say the least. But you, your vows of vengeance are so absolute that you would disrespect her. Her heart aches for you, and yet you show her total apathy and complete disregard. You said that you would marry her once you have fulfilled your task, but is that even something you, in truth, desire, or was it something you said dispassionately just so that your family would no longer bother you and distract you from your training? Actually, that was not a question. I already know the answer. Your mind is locked so deeply in the past that you have no imagination of the future. You have some vague idea that after you slay this demon your story will come to a close and you might settle down with Ritsu, but you are held by no conviction to this idea.
Well, stories do not end until the day we die, and for you, that day will not be today. They just keep going as we do. There are joys and hardships, defeats and victories, there are many things in life but you have allowed yourself to be consumed by just one thing, and yes, this thing is consuming you as we speak. I must say, your story is not unique. Many have suffered as you have, and many have allowed themselves to be destroyed by what tortures them. There have been many cases where people become so obsessed with one goal that they lose sight of everything else and reduce themselves to nothing in the process. Yet, you have not become nothing. You have become something far more sinister in your empty rage. Now stop scowling and heed my words.
The Tsujo was not destroyed the night that the rage beast attacked, but it will be destroyed the night you attack it. You can choose to embrace love and create new life, carry on your family lineage and hope to find happiness where it is known to be, or you can choose to embrace hatred to cause the death of that beast in the hope that you will find closure in a dark and lifeless place. You can fulfill the promise of procreation you have made to those who love you, or you can fulfill the promise of destruction you swore to a heartless demon. The only blessing that I can offer you is this," The priest said as he produced a marriage contract written on a bamboo scroll that Shikaeshi promptly tore to pieces, "And with that, I have nothing more to say." 
Without uttering a single word, Shikaeshi returned to the inn alone. His family was worried about the fact that he did not wish to speak on the matters that had transpired with the priest, but, nonetheless, they respected his privacy and they prayed he could move past what must be weighing so heavily on his heart. After all, it was the morning of the Celestial Festival, a time to prepare for a night of celebration and enjoy the divine gifts of the heavens. Shikaeshi had promised Ritsu that he would spend the whole night stargazing with her, but come dusk, he was nowhere to be found.
== Encounter ==
Shikaeshi faced the ruins of his old family home. He expected that by now it may have become overgrown with weeds and infested with all manner of wild creatures, and yet that was not the case. The ruins of the mansion before him were exactly the same as he remembered them that dreadful night. Not one blade of grass had grown and not one critter was stirring. On the splintered and exposed wood planks, there was no sign of rot or mold, and the few standing paper walls had weathered all the storms without so much as single tear. Even the crimson pools of blood were still fresh on the ground. Furthermore, behind all the devastation, the dirt trench that the contorted demon's writhing form had carved into the mountainside also lay untouched by all things natural.
After retrieving the bone katana from the place that no one else knew, Shikaeshi set foot on that path of barren earth as his eyes coldly traced the way up the mountain. Over twelve years had passed since so many he loved had perished, and now, as the luminous glow of the full moon and all the stars in heaven guided him, he prepared to face that which has tormented him for the past three-fifths of his existence. Shikaeshi grit his teeth as he ascended, his sharpened eyes did not once blink, his steel heart not once wavering, his grip iron firm around the hilt of his blade. 
There at the peak of the mountain, the vile rage beast awaited him. Shikaeshi readied his blade, but he paused as he realized that the demon did not appear to be acknowledging his presence. Indeed, the demon appeared to be almost in distress when he looked upon it. Its countless limbs were bloated and swollen to the point that they could not bend, and a sickening maroon sludge leaked from its thousand razory maws. Its engorged form wheezed heavily as Shikaeshi approached, and foul sludge burst from its mouths in a torrent with every step he took towards it. The creature had become so morbidly obese from feeding on on his wrath that now it was helpless before him. Shikaeshi cursed the wicked demon for its past misdeeds and cursed himself for his present foolishness and frenzy. At that moment, Shikaeshi knew precisely what would happen if he drove his blade into the beast, but in his enraged state, he could not stop himself. Shikaeshi allowed for nature play its course; with all his might and all his fury, with the skill of 4000 days of training and the frustration of 4000 nights of rumination, with a sword forged from his loved and lost and with his whole being devoted to their vengeance, he fulfilled the ten-thousand promises of revenge that his arrogance could not possibly allow himself to forget. He thrust the bone blade deep into the creature's core.
There was a blinding darkness that surged forth from the beast as Skiaeshi was bathed in his twelve years of wrath. His vengeance was fulfilled, but the void in his heart was ravenous; he could feel his body becoming warped as his hollow soul siphoned off the twisted demon's essence. There was nothing that he could do but scream in rage as he was transformed into the being now known as Gekami, the Rage God. And as his curses echoed far and wide, the torn bamboo scroll soared across the land and bound itself to Gekami, anchoring him in place on the mountain top. It was then that the mountain became known as Gekidoyama, and all through the surrounding hills, Gekami's roars of wrath still ring, causing men and beasts alike to lose their minds to the berserker's frenzy.