Despite fighting some of the toughest opponents in the Blue Sea, One Piece’s Roronoa Zoro has only lost a handful of fights. Similarly, Demon Slayer’s Inosuke has met some powerful adversaries on the battlefield and rarely gone home a loser. As a result of their success, both swordsmen are supremely confident in their abilities; so much so that if the two were ever to meet, they would surely end up challenging one another to a duel. The question is, after the gauntlet is dropped who would succeed in proving they are the better swordsman?
It wouldn’t be a mismatch. Zoro and Inosuke are both excellent swordsmen with deep fighting experience. While both are relatively young warriors, they each have been training in swordsmanship for most of their lives. Zoro began his training in the renowned Isshin Dojo. There, under the tutelage of one of the world’s greatest sword fighters, Zoro was able to develop a solid basis in how to use a sword. Inosuke did not initially have any formal sword-fighting training, but once he entered the Demon Slayer Corps, he received the best training possible for a swordsman of his time. Indeed, to be a Demon Slayer, he was required to master such techniques as the Total Concentration Breathing, which greatly improves a user's physical and mental abilities.
Early on, both developed unique sword-fighting styles. Inosuke created a style known as the Beast Breathing Style, which took advantage of the fact that he was raised by a pack of boars. The style is not very complex but, like an attacking boar, is direct, aggressive, and persistent. It does not allow an opponent to relax or mount a counter-attack, but rather presses them to relentlessly defend, retreat and succumb. Zoro’s style, which is known as the Santoryu Style, makes use of three swords, one held in each hand, and the third held in Zoro’s mouth. The style allows Zoro to make use of his inherent abilities of strength, speed, and in-combat tactical flexibility. As such, Zoro can simultaneously attack and defend at an exceptionally high level of skill.
Outside of their sword-fighting abilities, both have unique characteristics that they also integrate into their fighting styles. Zoro can tap into a higher level of consciousness that increases his power, strength, and speed to otherworldly levels. When in this zone, Zoro’s opponents feel like they are simultaneously fighting multiple adversaries attacking them from multiple directions. Conversely, Inosuke has a Spider-Man-like spider-sense that allows him to not only sense impending danger but also accurately map out people, demons, and objects in his immediate vicinity. However, one negative trait that each have is stubbornness. Both are very willful fighters who tend to resort to brawling in the heat of a fight rather than focusing on their strengths. This stubbornness has led both into bad situations that they might have normally avoided, but need to work twice as hard to resolve.
So, who wins in a fight? Since both can counter the other’s strengths, success will come down to experience. Both have deep experience fighting, but Inosuke’s is primarily focused on fighting demons. Zoro’s opponents, on the other hand, range from humans to animals to demons. Accordingly, Zoro’s body of work includes a range of fighting styles, theories, tactics, and body shapes. This will likely give him the edge in a fight against Inosuke. Being the veteran he is, One Piece's Zoro will be able to use these experiences to eventually overcome Demon Slayer's Inosuke and his somewhat simple, straightforward though dangerous style.