The Ultimate Demon Slayer Vol.1

the Kamado siblings

the two sisters returned to the butterfly mansion they were greeted by Aoi and the rest of the girls and they'd all have dinner together
As they were eating Kanae was wondering about who defeated uppermoon 2

Meanwhile with Ben
He was still flying as Jetray until he comes across a snowy mountain

Ben: this should be a good time rest up for today and hopefully I can figure out a way to go home

As Ben begun to rest he heard screaming and crying

???: Let my sister go please I'll make a cure for her to turn back into a human please don't kill her

Ben: What was that?

Ben heard the screaming and started to run towards it there he sees a man wearing the a black uniform and miss match haori he has black hair and blue eyes this was the water hashira Giyu Tomioka and a boy with red hair and red eyes and a burnt mark on his head this was Tanjiro Kamado

But that wasn't the only thing Ben saw he sees Giyu holding a girl that was growling and was trying to get out of his grip this was Nezuko Kamado

Ben: what's going on?

Giyu: this is good bye demon

Giyu was about to kill her as he stabbed her

Ben's eyes widened at this he was going through the Omnitrix to pick the right form for this one and he found one and slabbed it

As he transformed into a tall plant alien with the Omnitrix on his chest

"Swampfire" he shouted

Swampfiire: Hey get away from them

They turned around and they're eyes widened at Swampfire's appearance

Swampfire started to run towards Giyu and lands a punch on him

Swampfire: Are you alright?

Tanjiro: yes I'm alright thank you um Mr?

Swampfire: You can call me Ben but in this form I'm Swampfire

Tanjiro looked at him in aw and Giyu was getting up to

Giyu: "Goans" why are here demon

Swampfire: first of all I'm not demon and second of all who are you

Giyu:Giyu Tomioka

Nezuko stood in front of Ben and Tanjiro like she was protecting them from him

Giyu's eyes widened at this and sheeths his sword

Giyu:it looks like you're sister can control herself keep her away from the sun go to mount sagiri and see  urokodaki so he can teach you two breathing techniques tell him Giyu Tomioka sent you

Giyu disappears and left the two

Tanjiro: thank you Ben-san

Swampfire:No problem kid

Swampfire slapped the Omnitrix on his chest to turn back into his human form

Tanjiro's eyes widened as he sees a teenage boy with brown hair, green eyes wearing a green jacket, black shirt, blue pants and black and white shoes

Tanjiro: how did you do that?

Even Nezuko was shocked by this

Ben showed them the Omnitrix on his risk

Ben: it's called the Omnitrix it has the dna of over a million aliens

Tanjiro: Aliens? What's that

Ben: their beings from outer space

Tanjiro:why do they live in outer space when they can't breathe

Ben looked at him crazy

Ben: okay anyway oh yeah didn't get your name

Tanjiro:o-oh I'm Tanjiro Kamado and this is my sister Nezuko

Nezuko couldn't speak due to her wearing a mouth guard but she was happy to meet him

Tanjiro: Ben-san please can you come with us and become a demon slayer with me so we can turn Nezuko into a human

From what he can gather some one turned his sister into a demon and now he's asking for his help

Ben: alright I'll help you out Tanjiro

Tanjiro thank you Ben-san now let's go to the house

The three walked to their home what Ben saw horrified him he a little boy on the ground covered in blood walked towards him and when he turned his head he looked at the inside of the house and it looked like a massacre

Ben: who did this?

Ben and Tanjiro dug five holes for them and placed the bodies in them and begun to buried them

Tanjiro and Ben were praying for them and Tanjiro and Ben begun their journey.