So real quick, bit of information on Izuku and some other characters in this since there will be some things to know.

16 (Eyes are red with slits like a demon's that he learns how to change to a normal human's as he grew up.)

Hashira

Twin Nichirin Sword color: Dark Purple

Hand Guard: Solid blood red with the blade or handle looking as a pupil to emulate his own. As a way to honor his master, Izuku asked for a grip similar to a butterfly to be placed on the bottom of the handle that's held together by a chain.

Eyes of the Beyond

Izuku's Blood Demon Art is unique in ways that allow him to see the souls of those he gazes upon whenever he wishes. Along with this, he can also see the souls of those who are tied to the person as well as see what type of person they are or were in a demon's case. He is also able to tell if these souls were murdered by a demon depending on how they look when depicted to him.

Cursed Breathing

Cursed Breathing is a unique skill Izuku had created thanks to the abilities he's gained while training at the Butterfly Mansion under former Hashira Kanae Kocho. This Breathing allows Izuku to use his Blood Demon Art in conjunction with his fighting style. The technique holds 8 forms to which Izuku developed and perfected himself.

1st Form: Cursed Cross Purge. Izuku pulls one blade upwards with his other across his body to act as a cross to cut a demon two ways

2nd Form: Black Rotting Flames. Izuku uses the grief of the souls as kindling to light his swords before attacking. The area that is cut is singed shut with black flames for healing to be slowed down temporarily.

3rd Form: Heaven's Black Lightning. Izuku uses downward momentum to attack at speeds almost as fast as a Thunder Demon Slayer. The act creates the sound of lighting cracking for it to have it's name.

4th Form: Night Wind Current Slash. Izuku uses a spiral force to attack with it using crescent slashes to resemble a small tornado.

5th Form: Poisonous Rising Slash. Taking a tip from Shinobu's book, Izuku turns the grief of the souls a demon has tied to them into a deadly paralysis toxin that if administered enough can paralyze the nerves leaving them defenseless for an hour.

6th Form: Striking Demonic Slash. Izuku combines the rage of souls to create a slash that incites fear and intimidation towards most demons. If one is more powerful than the average then they can overwhelm this presence.

7th Form, God's Judgement. Izuku's blades burn bright with the feeling of the sun itself by gathering the hate brought on by the souls around. This could cause a demon to die if the attack misses the neck by an inch to increase the diameter he needs to get the neck between.

8th Form: Flesh Rotting Pierce. Izuku uses all the negative emotions in the souls around to use that to destroy the demon from the inside out. As long as the blades are still connected, the corrosion continues and can't be healed until it stops.

Sensory Detection:

Thanks to Izuku's ability as a demon, he can sense things that most Hashira would never be able to in the aspect he was a born natural. Added with his Blood Demon Art, Izuku is able to scout and detect where demons are a distance away as well as the level of danger they pose.

Enhanced Physical Abilities:

As a half demon, Izuku's body is more durable than a normal human's and can heal faster. Due to his half demon nature though, he is far weaker in natural strength and healing. Shinobu theorized that this may have something to do with him not drinking human blood yet or eating a human to offer him the chance if he'd like to drink blood to help with Izuku immediately refusing to avoid possibly losing his humanity. He does not know if he can regrow a severed limb and dares not try knowing if it is gone, it can be gone for good.

Tactical Skills:

As a Hashira, Izuku is able to make combat decisions quickly and act on them in less than a second to avoid casualties.

Medical Skills:

Thanks to his upbringing with Shinobu and Kanae, Izuku learned pharmaceutical knowledge as well as first aid to some degree in order to help avoid injuries to be more serious. It is not at all near skilled enough to relate to Shinobu, so he doesn't use it much when with her.

Mitsuri Kanroji

Ochako Uraraka

Momo Yaoyorozu

Alright, that's it. Also, few questions before this story officially starts.

I plan to make Momo and Ochako Demon Slayers taught under Izuku in this story when he gets to UA and goes undercover. What should their Breathing styles be? They cannot be Cursed Breathing since it was made for only Izuku to use. Also, should Shinobu and Mitsuri know of them before Izuku reveals his true identity? Lastly, would anyone want lemons in this story? Figured I'd put that out since the story will go forward in some ways depending on that.

Leave your comments on what you think down below and I will start this story in the next few months. Hope you all enjoyed and thanks for reading.