In "Demon Slayer," the Thunder Breathing technique is significant because it is one of the five main breathing techniques used by the Demon Slayer Corps to enhance their combat abilities. Each breathing technique grants unique powers and skills to the users. Thunder Breathing specifically focuses on speed and agility, allowing the user to move swiftly and strike with lightning-fast attacks. It is considered a powerful and versatile technique that is crucial for demon slayers in their fight against demons.