The Tenth Pillar. (Kimetsu No Yaiba X OC)

The outcome of the battle.

Hiiro plummeted into the ground. Sweating and smiling. He did it, at last, after a long painful training. He achieved the Bankai.

"At least, I thought you won't make it." The white haired Hiiro mocked.

Currently, Zangetsu and his doppelganger were manifested, the two spirits of the black blade could get a physical body to help the young shinigami.

"You did good, Hiiro." The black coat man encouraged.

He was indeed, proud of the boy, he burned himself out during the training. Even when his body found himself at the verge of breaking, Hiiro could break those limits, over and over again, until he achieved the ultimate technique.

"It's all thanks to you two. You've guided me, until now." The black haired boy smiled to the two parts of his Zanpakuto. "You saved me back then when I first fought against Kokushibo, and now you even granted my selfish desire."

The two spirits laughed, not a mocking one, but a comfortable and warm laugh.

"I don't care helping out" the black haori Hiiro replied. "I can kick your ass everytime you need to train."

The three of them stood up. Hiiro Kojima, the night pillar took the black blade on his hands. His Zanpakuto, his friends.

"Hiiro" Old man Zangetsu called. "I shall tell you, the name of your Bankai. Two spirits live inside the black blade. Your Bankai is divided into two. But the name is the same."

The man in black robes took a step forward. Looking straight at Hiiro's eyes. Like he wanted to pierce his soul with a single gaze.

"The name of your Bankai is..."

"Tensa Zangetsu. First Night: Hollow Moon."

Hiiro Kojima smirked as he studied his dual blades, the two spirits inside of him, lending their powers to him.

"What are those?!" Kokushibo barked as he retreated, his eyes couldn't see any other than the new sword of his nemesis, one was gigantic, as big as his flesh sword while the other one was clearly smaller. "What's that Bankai thing?"

The night pillar ignored the uproar of his enemy. He felt his own power flowing through his veins, it was on a completely different level.

"Answer me!" With a violent swing, the whip-like attack reached the human. With a successful hit, a dust cloud raised from the battlefield. The demon began to laugh "So much for a weak power!"

The cold steel pressed against his throat. His six eyes opened wide and his jaw almost dropped to the ground. The small black Khyber knife was pushing against his weak point.

A cold golden glare came from the tenth pillar of the demon slayers corps.

His lips pressed against each others. The only thing that was shown on his face was the killing intent towards Kokushibo.

'When did he moved? I couldn't even catch a glimpse of his moves?'

As is body shivered out of fear, the golden gaze of his foe pierced deep inside his soul.

"Don't underestimate humans, Kokushibo." Before the Upper Moon could create distance between them, a swift slash created a big cut in his chest.

Even though Kokushibo was fast, his moves seemed slow when compared against the pillar's speed. Lime a wild animal, he rushed and like a tiger, he threw a violent hurricane of heavy slashes.

Slowly the former demon slayer found himself unable to fight back, yes indeed, he was losing his ground against the swordsman.

He felt the hate rising inside him, clenching his teeth as he blocked the wild barrage. The demon tried to found an opening to counter, but he found none.