Izuki made good on her word and returned to the park again the following evening, finding herself enjoying the tales of the apparently unknown Quirkless heroes Hebi knew of. Unbeknownst to the greenette, the people that Hebi was talking about weren't Heroes, or Underground Heroes, as Izuki knew the term, but Demon Slayers from both earlier eras and more recent ones. A few of the ones Hebi mentioned that Izuki found particularly interesting were a few from the Taisho era. More specifically, Kyojirou Rengoku, the Flame Hashira, Shinobu Kocho, the Insect Hashira, Tengen Uzui, the Sound Hashira, Tanjiro Kamado and Zenitsu Agatsuma, for various reasons.
After about a month of listening to the stories and exploits of the Quirkless Heroes, Izuki asked Hebi the question that the Demon knew from the start that the greenette would eventually ask her. Could Izuki learn the techniques of the Demon Slayers and become a Hero with those techniques? After some hard thinking, Hebi told her that she probably could if she trained and turned her weak body into the body of a warrior. And thus began five years of training from hell.
One of the first things that Hebi had Izuki not only learn but also master to the point where she was subconsciously doing it in her sleep was Total Concentration Breathing, Total Concentration: Constant and Recovery Breathing, literally. Which was actually somewhat easier for Izuki than most people thanks to her Quirk Air Filter and her abnormally large lungs. Alongside developing her physique, thanks to more basic and normal training methods, something that Hebi and Izuki worked on constantly was the creation of a Breathing- and fighting style unique to Izuki. Taking full advantage of Izuki's Quirk, flexible build, talent for acrobatics and gymnastics, high dexterity and the fact (as they discovered early on) that Izuki was ambidextrous, they succeeded. Smog Breathing. A highly acrobatic style that revolved around dual wielding a pair of cleavers with bandages wrapped around the handles and the wielder's wrists for extended range and maneuverability. While most of the Breathing style could potentially be adapted for others with similar skills and abilities, what made the style truly unique to Izuki was how her Quirk Air Filter was incorporated. Smog Breathing made high use of smoke and various gases, which Izuki wouldn't breathe in thanks to her breathing through her gills, keeping the smoke and gases from entering her system.
As the entrance exam for UA high school closed in during the fifth year of training, Hebi gave her student a gift for the entrance exam. A proper set of cleavers for Izuki to use during the exam. While the cleavers weren't Nichirin Swords, they were made out of one of the toughest metal alloy around, making them fully capable of cutting through most materials with some effort, including steel.
