Regeneration of a ghost

Kimetsu Academy

After the battle with Muzan back in the Taisho Era, the demon king had been killed, restoring peace.

Even though the demon slayer corps was dibanned but demons are still lurking around in the dark. 

The Ubuyashiki family think that the demon slayers are still out there to help with the situation and gather them together in Kimetsu Academy. 

Little do they know that someone is paying them a visit...

It's a normal day in Kimetsu Academy, everyone is in class, teachers are walking around, until Sanemi falls into one of the trap that [Y/N] set up for intruders.

"WHAT TH-?!" He is now hanging upside down on a tree branch, right outside the first-years classrooms.

Inosuke who was staring at the window and saw the whole thing, he then shake his seatmate chair which is Zenitsu while pointing out the window to show him their teacher miserable state.

"MONITSU LOOK, LOOK!! HAHAHA!" Zentisu look over with a annoyed look but faded as he see his teacher hanging outside while cursing at the rope.

They both laugh at the scene while Tanjiro is confuse at what are they laughing at.

"What are you two laughing about?" 

Inosuke pointed outside towards the hanging Sanemi and Kanae who is helping him down from the trap.

Kanae: Ara~ Sanemi-kun, be careful next time. 

Sanemi: There will be no next time!

[Y/N] [L/N] one of the youngest teacher enter the classroom. They teach the young swordsman different breathing from their ancestor and different types of blood demon art. Basically a history teacher.

They also happen to be a regeneration of their ancestor, [Y/N] Yugi, a ghost that assisted the demon slayers during the battle with Muzan in her human form. 

"What are you three looking at?" They asked. Tanjiro notice the [boy/girl] and drag the boys back to their seat. 

"Nothing sensei!" Zenitsu yelp in fear.

Inosuke put both of his leg on the table, Kanao greeted [Y/N] so did Genya.

"Ok, please return to your seat then." They flipped open the book in their hands and turned to the page about Flower Breathing. 

"We're learning about Flower Breathing today, the breathing that Kanae-san and Kanao-san used. And we are practicing that today." Zenitsu jumped since every time [Y/N] teach them new breathing style, they would bring them to the gym and started her training. 

Which means that they have a 1v1 training against [Y/N]. Tanjiro grab his wood sword and strike first. [Y/N] jumped 5 feet in the air and hit the boy back to the ground with her own sword. 

"Not bad, still need to watch your enemy move while you strike. In other words, good job. Next!" Zenitsu is scared that he won't make it after the training so he hid behind Nezuko. 

"NO WAY I'M DOING THAT! YOU'LL JUST KILL ME! NEZUKO-CHAN PROTECT ME FROM THAT DEMO-" 

"Ara Ara~ Who do we have here~?"

Let's just say that Zenitsu got dragged away by Shinobu who was passing by.

"Kanao-san would you like to do the honor of showing your classmate the Flower Breathing?" [Y/N] said.

"Yes, sensei. "  

The gym did got destroy but [Y/N] fix it with her cursed technique. 

Cursed technique: Reverse Healing 

The User can reverse any damage, that includes body parts city destroyed damaged. Drawback is that it'll drain the user's energy while results headaches, fainting and possible coma.

[Back at the teacher's lounge]

[Y/N] went back to their seat and sigh in relief after they finish fixing up the gym. 

Rengoku: You did well today, [Y/N]-san!

[Y/N]: Thank you Rengoku-san! Now if you don't mind, I'm gonna have a little nap.

Suddently, they felt a waved of danger coming from behind and snap their head toward the intruder. 

Turns out it was Sanemi. 

"Good afternoon, Sanemi-kun. How can I help you?" the [boy/girl] laid on their desk, tired. 

Sanemi hold up the rope that was a part of the trap.

"WHY THE HELL WOULD YOU SET A TRAP UNDER A TREE?!" [Y/N] gave a bored look a him while Mitsuri ran in the room as well.

"[YYYYYYY/NNNNNN]-CHANNNNNN! HEAR ME OUT! HEAR ME OUT! THERE'S NEW STUDENTS JOINING US!!!" Mitsuri said while shaking them. 

"OI!" Sanemi shouted. 

"Eep! Sorry Sanemi-san!" and there she ran to teach the second years.

"NOW TELL ME WHY YOU DID THIS?!" 

"To prevent intruders. Shinobu-san suggest me to put it there since that's a blind spot and an easy way for demons to sneak in." Sanemi just scoffed at the statement.

"I'll see you tomorrow Sanemi-kun. I need rest." and they fall asleep on the desk.

Sanemi put the rope on the desk and left. 

[In y/n's dream]

A dark void surround them as the same girl from before appear in her dream.

She wore some sort of ninja gi as her [E/C] met their own. 

"You're here too huh?" the [boy/girl] spoke.

"Yep. Still don't know why am I here." the girl chuckle. 

"You know that our grandmother is not dead yet, and we both have a guardian in our head."  

Luna appear in her usual clothing and hit the girl on the head. 

Luna: I heard you're talking smack about me.

[Y/N] notice some light shining in a distance and told the two that they need to leave since they are waking up.

"See you next time, [Y/N]!" the girl exclaim.

"You too, [L/N]" They said back.

[Back to reality]

[Y/N] woke up from her sleep due to the loud sound. Just a few seconds later, three kids barged in the teacher lounge

Rengoku: Hello, kids! Never seen you three here before!

Shinobu: What's going on here~?

Then footsteps were hear throughout the hallway as Sanemi and Uzui barged in as well. 

"Can you all stop barging in the door, I'm trying to sleep." The attention shift to the [boy/girl/non-binary pals/trans pals] which made them shot a rubber bullet at both Uzui's and Sanemi's head, using her gun.

"WHAT WAS THAT FOR?!/ That hurts [Y/N]!" Sanemi and Uzui shouted.

"For barging in even though I told you I'll be sleeping. Fyi I'm not paying for the damage, Gyomei-san" they said to the supervisor who is standing outside the door.

"Understandable [Y/N]. Sanemi, Uzui, both of you need to pay for the damage you cause." The two nodded.

"Now, you three are the new students right?"