Summary
Inosuke's unique nichirin blades are serrated due to his Beast Breathing technique and aggressive personality. The serrated blades are both aesthetic and functional, resembling the jaws of an animal in a more menacing and damaging manner. Inosuke forged the serrated blades himself, demonstrating his skill and preference for using fearsome-looking blades.
Thanks to their colorful designs and personalities, it is easy to distinguish the characters in Demon Slayer. When it comes to the Demon Slayer Corps, it seems they are given a lot of freedom in customizing their outfits and weapons. In Inosuke's case, his untamed personality may not leave them with any other choice. Not only does he wear a uniform, he also wields two serrated nichirin swords.
Inosuke isn't the only one with a special weapon. Love Pillar, Mitsuki Kanroji has a whip-like nichirin sword, if it can even be called a sword, but regardless, it's still a regular, even sword. The same goes for the other members of the Demon Slayer Corps whose weapons are different from a normal looking sword: the blades are still flat and even.
The Nichirin Sword is special to all demon hunters
The importance of swords is pushed throughout the series; especially in how they define certain characters.
The Nichirin Sword is a fictional katana specifically crafted to slay demons. They are crafted with two legendary ingredients: Scarlet Crimson Iron Sand and Scarlet Ore, said to absorb and transmit sunlight, thus having demon-killing properties. It is said that the color of the blade changes when a demon hunter first swings the weapon, and this color is tied to their breathing technique. Inosuke's nichirin sword is indigo grey, characteristic of his Beast Breath technique, of which he is the only known user.
Nichirin swords are meticulously crafted in the blacksmith village, a location kept secret throughout the series. However, in episode 25, it is shown that Inosuke did not receive the serrated sword, and in fact, He was the one who forged the saw teeth out of stone.making Haganezuka extremely angry. Coupled with his boar head and the fact that he walks around shirtless, Inosuke has without a doubt the strangest appearance of all the demon slayers.
Why does Inosuke's Nichirin sword have a serrated blade?
Koyoharu Gotouge made sure that the aesthetic choices made sense as well.
The reason Inosuke's blade is serrated makes sense both in terms of character design and coherently relates to his personality and lore. The serrated blade looks ferocious, which ties into Inosuke's general “wild” attitude.. Just like all the girls in the Butterfly Mansion wear butterfly-themed hair accessories to reinforce how they evoke, the serrated swords are a complement to his character. Not only that, they lack a proper handle. They are simply wrapped in several layers of bandages so that Inosuke can wield them without cutting himself.
In Official Fanbook: Demon Slayer Corps Records, Gotouge states that Inosuke likes these menacing-looking blades because they also resemble the jaws of a threatening animal. A similarly serrated blade will also do more damagesomething that can be appreciated in real life when trying to cut a steak with a serrated knife compared to a regular knife. A sword like this would require more maintenance, but Inosuke was certainly very capable of doing this if he made such swords himself in the first place.
Inosuke is a very skilled member of the Demon Slayer Corps, his strength and intuition have helped him win his battles. His twin serrated swords highlight his rough and bold nature. Author of Demon slayerKoyoharu Gotouge, has done an amazing job of giving his characters visual elements that match their identities and personalities.