Train and then Train some more!

Yami woke up, he was still hugging the sword and he was covered in blood. He looked at Nezuko, who was healing him. He took out a potion and drank it before slowly getting up from the ground and looking at his cut up scarf. He sighed sadly and stumbled along, being led by Nezuko to the rest.

He gave them healing potions before being brought to Tengen. He looked at Tengen, who had bandages over his left eye and arm. He held out a healing potion and Tanjiro said "He said 'Drink this.'" Tengen drank the healing potion and his wounds disappeared, but his hand and eye were still gone.

Yami dug in his backpack and pulled out a metal disc. He grabbed Tengen's arm and tore the bandages before cutting the healed flesh, the girls shouted "WHAT ARE YOU DOING?!" Yami waved and sent them away as he fastened the disc on Tengen's nub and tightened it.

He tapped on it and nodded, Tanjiro was stunned and said "He said 'Think about your hand or anything you want. Nothing living though.'" Tengen looked at the metal disc and thought about his left hand. The nano-bots made a hand and Tengen's entire world view was destroyed by the metallic hand he was looking at.

He said "W-W-What is this!?" Yami nodded and Tanjiro explained "It's called a Nano-Prosthetic, his dad made it he has a bunch on him just in case." Tengen wiggled his fingers in a complicated manner and he was stunned as he said "My hand... I can move my hand!" Yami nodded and Tanjiro explained "It's called Phantom Limb Syndrome, even if there's nothing there you will be able to feel that there is. The prosthetic uses this syndrome to control the movements of the hand. It works the same way as a normal hand except it's made of metal. It can also become anything else you can imagine."

Tanjiro himself was stunned and Tengen's hand became a kunai, his mouth made an 'O' and Yami got up before stumbling away, hugging his sword. Yami waved and Tanjiro said "Right! I almost forgot!" as he ran off.

Yami continued walking before finding the demons' heads, he was basically unconscious right now. He took out his sword and sliced both heads in half before walking away and sheathing his sword and hugging it as he fell to the ground.

Hiro appeared and held him up, Zerotwo appeared next to him and smiled "What a good boy." Hiro smiled slightly saying "He's not too bad." he looked over behind him at Tengen and said "He's kind even though he doesn't show it." Zerotwo smiled and Hiro added "I only gave him two prosthetics." she looked at Tengen and smiled, she walked over and crouched in front of Tengen, smiling "Hello."

Tengen said "Who are you? What are you doing to the kid." as he reached for his sword, Zerotwo giggled and said "I'm his mother, I can do whatever I want to him, no?" Tengen looked at her and she lifted his bandages on his eye before clicking her tongue and saying "Poor boy..."

She ran her finger over his eye and her finger glowed green, she stood up and said "Keep it up, thank you for saving my son." Tengen opened his left eye and he found that he could see! He was in awe and asked "Are you a goddess?"

Zerotwo pursed her lips and replied "If you would like to think so." before walking away. Tengen was dazed, he didn't know that anybody saw him do that. Just before the demon's body exploded, he kicked Tanjiro and slapped Yami back out of the way from the blood blades, taking most of the damage himself.

That's why Yami's scarf was just cut up and he didn't have major wounds. The same with Tanjiro.

Hiro held Yami in his arms and smiled "You're making me more and more proud every day, kid." he pressed on Yami's forehead and unlocked both Hakis before pouring a bottle of purple liquid down his throat. It was a poison resistance potion Hiro made. He tried it on himself first and it worked.

He laid Yami down on a wall and kissed his forehead, Zerotwo caressed his cheek and said softly "Mommy loves you, continue working hard baby." before they both disappeared again, Hiro manipulated Tengen's memories to not know that Yami was Zerotwo's son, but that was the only thing he changed.

Tengen basically believed a Goddess came down and healed his eye for killing the Demon.

A few days later

Yami woke up in a hospital bed in the Butterfly mansion, he was still hugging his sword, they literally could not take it from him, no matter who tried to take it. Eri lunged at him crying "Brother~!! You're awake!" Yami coughed and said "What happened?"

Eri cried "You fell unconscious after killing the Upper Moon 6 demons! You're a big shot! But you were asleep for 2 days!" Yami got out of bed and said "2 days of missed training..." Eri slapped him into the ground, shouting "WHAT DO YOU MEAN TRAINING YOU SHITTY BRAT, I'M GOING TO KILL YOU BEFORE ANY DEMONS CAN IF YOU WALK OUT THAT DOOR! I SWEAR TO GOD, YOU DAMN PUNK! TRY ME!"

Yami groaned with his face stuck to the floor. Eri picked him up and said "REHAB TRAINING!" before dragging him away, Yami mumbled "Why are you so strong..." Eri ignored him and threw him to the wolv- the little girls, who started stretching him in various positions.

Yami didn't make a sound, just got stretched while hugging his sword. He was extremely limber, Tanjiro and the other two started rehab training after a few days when they woke up. The group of 4 were training and Zenitsu, Inosuke, and Yami were sent on missions after 2 weeks of rehab.

Quickly in a cycle like this, 2 months passed.

Yami noticed that there were more metal discs and a box of weights in his backpack. He wore the weights at all times and shared with the other 3, they each had 4 weights on their wrists and ankles at all rimes even when eating.

Zenitsu and Inosuke were out on a mission and Yami was preparing for a trip to the Swordsmith village. He over heard word of a training dummy there and he wanted to go check it out. He sent a crow to the big boss, who allowed it and congratulated him on his take down of an Upper Moon.

Yami thanked him and was about to leave when Tanjiro said that he was coming too since he still didn't have a sword. They left together, being carried by Kakushis with all their senses blocked because the location was a super ultra mega secret.

*MORE STONES! AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH!!!!!!!!*