Zenitsu appeared to be passed out, but he could feel the grass and heard, "im sorry I had to go, please take care of Kaigaku Zenitsu." it was gramps.
"I promise gramps," he said.
Soon, he woke up in the snow seeing kaigaku next to him with a muzzle on.

He heard a familiar voice, and he looked up to see the same girl from earlier.
"There's nothing really much I can do but to say that you need to try hard and keep on fighting for your brother" she said clear sadness was in her voice, "my best bet is go to the mountains and train" she spoke, "you should hurry you were lucky that its a cloudy day, I'm sorry I can't do much to help you" she bowed and then she started to leave.
"Thank you!" He cried out.
Soon, Kaigaku woke up, and they both walked up to the house they lived in and buried there master and collected some stuff.
Zenitsu prayed for his gramps, and soon they both left, taking her advice and heading up a mountain.
Traveling with Kaigaku was hard because he was a demon and once the sun appeared they hid in a cave so he decided while Kaigaku was in the cave sleeping he would go out and train and at night they would travel to the mountains sometimes Kaigaku had to carry him.
Even though Kaigaku has turned into a demon, his personality remains no not his mean one where he would hit and yell at Zenitsu but more like a nagging mom type of thing.
Because this one time while they were traveling at night he saw a pretty lady and tried to flirt with her and he almost got stabbed by Kaigaku because of his terrible flirting and idociy because that woman was already married.
Soon zenitsu started to use a basket to carry Kaigaku around, it wasn't easy to convince him to get in it at first but after hours of whining and coming up with good reasons he decided to give in.
When they finally got to the mountain, it was pure hell for zenitsu because the air was thinner, and he had to run up and down the hill 20 times because Kaigaku "encouraged" him too.
He went over the basic moves and swung his sword over 100 times yet he wasn't able to learn any other forms, he needed kaigaku's help but he can't because he's been asleep for a few days now and he's kinda getting worried but he shooked it off and kept training.
"Ahh, finally done for today," Zenitsu thought as he went to the cave to sleep until he heard a bloody scream waking kaigaku up.
Kaigaku looked in the direction of the scream and took his sword and dashed off into that direction, "kaigaku, wait!" Zenitsu said as he was chasing after him.
Luckily, he jogged up and down the mountain 20 times a day, or else he wouldn't be able to catch up with him.
When they got there, Zenitsu heard something bad. He looked up and saw a demon eating people in a temple.
He was terrified he wanted to scream, but it didn't come out, The demon smelled them and stopped eating the corpse and looked over at them with a grin on his face.
"My my, you look delicious," he smiled, but when he saw Kaigaku, he glared, "Oi, this is my territory, so beat it," he said, kaigaku only glared back.
The demon was about to attack them, and Kaigaku had prepared his sword to behead the demon, but then his head was knocked off, Zenitsu screaming at the sight.
"Hey, are you two okay?" He heard an angelic voice. He looked over and saw a boy with handfua earrings running over.
"My saviorrr!" He cried grabbing onto him snot going on his clothes, "uhm your welcome" he says, "you little bitch!" The now beheaded demon said.
They all looked over and saw the demons head on the ground as the body was moving towards them, "oh shoot what do we do what do we do!" Zenitsu said looking at the boy for help.
"Uh I don't actually know" he said chuckling nervously.
Zenitsu gulped as the demon arm reached for him but it got sliced off thanks to Kaigaku.
"Why the hell are you guys protecting humans!?" The demon head roared, "I'll deal with the body you deal with the head" Zenitsu said to the boy and went off to help the girl and Kaigaku.
Kaigaku and the girl were fighting off the demon body which wasn't really hard for them until they accidentally got caught off guard and tripped almost falling off a cliff, with all his energy Zenitsu ran up yelling "NOOOOOO" and tackled the demon's body off the cliff letting it be devoured by the river he would've been with the body if it wasn't for Kaigaku grabbing his haori.
Kaigaku brought Zenitsu up to the surface while the girl also proceeded to help him up.
They quickly went back to the boy and saw him with a demon head that looked like it was passed out.
"W-what do we do what the head?" The boy questioned, Kaigaku quickly came up and stabbed it with his nichrin blade and it slowly disappeared.
The boy looked a bit surprised by soon had a relieve smiled and sat down on a rock and introduced himself.
"I'm Tanjiro Kamado and this is my little sister Nezuko Kamado" he said and the girl just nodded, "o-oh nice to meet you Tanjiro I'm Zeintsu Agatsuma and this is my Aniki Kaigaku Agastuma or Inadama" he introduced himself while Kaigaku just glared.
"Hey is your Aniki a demon?" Tanjiro questioned, Zenitsu went silent but nodded his head, "he and my master were attacked while I was away" He said not wanting to remember what happened, "o-oh same thing happened to me" Tanjiro said also not wanting to remember.
"O-oh we should be going it's almost sunrise but it was nice to meet you Tanjiro" Zenitsu smiled again and soon he and Kaigaku dashed off back to the place they stayed at.
YOU ARE READING
Kaigaku and Zenitsu
Fanfictionwhat if Kaigaku changed into a demon earlier in the story when they were still training to become demon slayers. Cover goes to my friend Coffee