MHA Story And Quirk Ideas

Story: Demonforged Swordsmenship

Tanjiro dies of old age. He had mastered every breathing technique he could. [Moon breathing was a no, the only one that could teach him it is dead] He expects to be sent to heaven or hell. What he didn't expect was for God to show him that Muzan reincarnated into whatever this "MHA Verse" is and give him a choice. Reincarnate and ovveride Izuku Midoryia to stop a horrible future where Muzan uses his reincarnate, Tenko Shimura to rule over all humans, or proceed to heaven. Tanjiro choses the third option. Give Izuku Midoryia parts of his personality as well as his memories through his reincarnation, but never completly override him and watch Izuku go about things as a silent spectator. [Tanjiro does override a few things about Midoryia, like his self esteem and that natural awkwardness he has]
[Tanjiro gave Izuku his courage, his gentleness (the way Tanjiro could just naturally calm others down), and his confidence (Self-Esteem)

God tells Tanjiro that he and Izuku have until Izuku is 15 before Muzan fully awakens inside of Tenko, and that no powers will be transferred between the two realms, meaning that Muzan is without his demon powers and Tanjiro's Techniques may not work the same there.

Izuku's family is decended from a random ass samurai. As such, his katana has been passed down for centuries. Its still a perfectly good and sharp blade despite its age.

After inheriting Tanjiro's memories at four, Izuku quickly finds out that Breathing Techniques work differently in this world. They revolve around someones' Quirk Ancestry. Since Izuku's father had Fire Breath it means he leans more towards fire-based breathing tequniques like Sun and Flame Breathing. Flame Breathing is easiest for everyone with fire quirks and Sun Breathing is downright impossible for anyone who was born with a quirk. Only the quirkless can weild Sun Breathing.

If a direct, close relative has a quirk that is similar to the breathing tequnique then they'll be eligible to use it. If you are quirkless then you are a blank slate, and can use and effectively learn every tequnique without issue. That isn't to say that you can't learn an unrelated tequnique with the wrong quirk ancestry, but it would take literally 5× the amount of effort and practice. [So basically if you, your parents or your grandparents had a water-based quirk (This ranges from water minuplating quirks like Kota's to water-based mutation quirks like Asui's) you'd be eligible to learn Water-Breathing.

That also means that it'll be harder to learn a diffrent tequnique that you don't have in your leaniage, like Thunder-Breathing. This does unfortunately mean that if you don't have a quirk like that in your direct quirk anstrey you can't learn any special or elemental breathing tequniques as easily as someone who did would. If you have any type of Ancestry that correlates to any type of breathing tequnique, even if there multiple like let's say izukus granpa could breathe lightning and his grandma on his mother's side could control water. That would mean he'd have an aptitude for Fire, Water and Electric type Breathing Tequniques. However Beast Breathing is by far the easiest for everyone to learn, no matter what their quirk ancestry is. After all Humans were born from and at times, act like beasts.

Izuku received a Nobel Physiology Prize for discovering that Quirks weren't the only thing to have evolved 200 years ago! It turns out that the Muscular Structure evolved into something fierce! Minor Strength and Speed Quirk level strength and speed are now the norm if you go through a very harsh training regimen! It also turns out that the Appendix evolved as well! Now it stores a type of energy that Izuku's Breathing Techniques pulls on to [for example] light aflame a sword when someone's quirk is super strength. Or send water out for Water Breathing. Mostly it recycles the unused energy from the attacks, but the best way to grow and expand the energy it can hold is by eating a special fruit Izuku crossbreeded using a pineapple and a lily he calls the Powerlily.

[Imagine the stems I circled replaced by a pinapple]

Izuku's Breathing Tequniques are considered a new form of highly dangerous martial arts. As a result, they get treated as if they were quirks and those who learn tequniques from under him are put on a list along with what Breathing Tequnique they learned. Aizawa is one of Izuku's best deciples, having been a prodigy at Beast Breathing. Every time someone successfully learns thier first breathing tequnique they are given a sword made from the [previously] unknown metal source from the top of Mount Fuji.

[This is a natural blend of metal. The steel that makes nichireen blades don't exist in MHA. So getting it from atop a mountain is more a tradition than anything.]

Making new Breathing Tequniques that cater to a person's quirk is possible, however it's extremely hard. [So making a Copy Breathing Tequnique for a Copy Quirk, or a Blood Breathing Tequnique for a Blood Quirk is possible, but highly difficult to do, as it's not highly understood how it exactly works yet.]

Throughout all of this, Tanjiro watches through Izuku's eyes. If Izuku gets OFA, Tanjiro will meet the forebearers and they too will watch through his eyes. Tanjiro is basically a spirit living and sharing Izuku's body. With OFA he'd get sucked in and then a connection would establish. When it's time, Tanjiro would be able to speak to Izuku through OFA.